Fix unreadable event text when a calendar's color is white/very light

The month view rendered each event's text (and its little leading dot)
in the calendar's own color, on a very lightly tinted (~13% opacity)
background of that same color. For a light color like white or pale
yellow, the text ended up effectively invisible against its own
near-white background.

internal/web/templates/calendar.templ: add eventTextColor(hex), which
darkens colors above a perceived-luminance threshold (keeping the hue,
e.g. white -> a mid gray, pale yellow -> olive) while leaving already-
legible colors untouched; used for both the event text and its leading
dot. Also add a subtle ring to the event dot and to the calendar legend's
color swatch so a white/near-white swatch stays visible against the
page's white background, independent of the text-color fix.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

internal/web/templates/calendar.templ

@@ -1,6 +1,8 @@
 package templates
 
 import "fmt"
+import "strconv"
+import "strings"
 
 // CalendarSummary is one calendar (own or shared) shown in the combined
 // month view's legend.
@@ -119,7 +121,7 @@ templ MonthView(username string, data MonthViewData) {
 
 templ calendarLegendRow(c CalendarSummary) {
 	<div class="px-4 py-3 flex items-center gap-3 text-sm flex-wrap">
-		<span class="w-3 h-3 rounded-full shrink-0" style={ "background-color: " + colorOrDefault(c.Color) }></span>
+		<span class="w-3 h-3 rounded-full shrink-0 ring-1 ring-inset ring-black/10" style={ "background-color: " + colorOrDefault(c.Color) }></span>
 		<span class="font-medium">{ c.Name }</span>
 		if c.Shared {
 			<span class="text-xs text-gray-500">shared by { c.Owner }</span>
@@ -155,10 +157,10 @@ templ monthDayCell(day MonthDay) {
 			<a
 				href={ templ.URL(eventLinkURL(ev)) }
 				class="block truncate rounded px-1.5 py-0.5 text-xs hover:opacity-80"
-				style={ "background-color: " + colorOrDefault(ev.Color) + "22; color: " + colorOrDefault(ev.Color) }
+				style={ "background-color: " + colorOrDefault(ev.Color) + "22; color: " + eventTextColor(ev.Color) }
 				title={ ev.Summary }
 			>
-				<span class="inline-block w-1.5 h-1.5 rounded-full mr-1" style={ "background-color: " + colorOrDefault(ev.Color) }></span>
+				<span class="inline-block w-1.5 h-1.5 rounded-full mr-1 ring-1 ring-inset ring-black/10" style={ "background-color: " + eventTextColor(ev.Color) }></span>
 				if !ev.AllDay && ev.TimeText != "" {
 					<span class="font-medium">{ ev.TimeText }</span>
 				}
@@ -175,6 +177,55 @@ func eventLinkURL(ev EventSummary) string {
 	return "/web/calendar/" + ev.CalRef + "/" + ev.ID + "/edit"
 }
 
+// eventTextColor returns a color derived from hex, darkened if needed so
+// it stays legible as text on monthDayCell's very light (~13% opacity)
+// tinted event background. Without this, a light calendar color like
+// white or pale yellow renders its own event text as invisible or
+// near-invisible, since the same color is used for both the tint and the
+// text. Colors that are already dark enough are returned unchanged.
+func eventTextColor(hex string) string {
+	c := colorOrDefault(hex)
+	r, g, b, ok := parseHexColor(c)
+	if !ok {
+		return c
+	}
+	// Perceived luminance (ITU-R BT.601).
+	luminance := 0.299*float64(r) + 0.587*float64(g) + 0.114*float64(b)
+	const maxReadableLuminance = 170
+	if luminance <= maxReadableLuminance {
+		return c
+	}
+	// Scale each channel down so the color darkens towards black while
+	// keeping its hue, ending up comfortably below the threshold.
+	scale := maxReadableLuminance / luminance * 0.75
+	return fmt.Sprintf("#%02x%02x%02x", clampByte(float64(r)*scale), clampByte(float64(g)*scale), clampByte(float64(b)*scale))
+}
+
+// parseHexColor parses a "#rrggbb" string into its red/green/blue
+// components. ok is false for anything else (including 3-digit shorthand
+// hex, which colorOrDefault/hexColorRe never produce).
+func parseHexColor(s string) (r, g, b int, ok bool) {
+	s = strings.TrimPrefix(s, "#")
+	if len(s) != 6 {
+		return 0, 0, 0, false
+	}
+	v, err := strconv.ParseInt(s, 16, 32)
+	if err != nil {
+		return 0, 0, 0, false
+	}
+	return int(v >> 16 & 0xff), int(v >> 8 & 0xff), int(v & 0xff), true
+}
+
+func clampByte(v float64) int {
+	if v < 0 {
+		return 0
+	}
+	if v > 255 {
+		return 255
+	}
+	return int(v)
+}
+
 
 
 templ EventForm(username string, data EventFormData, errMsg string) {

internal/web/templates/calendar_templ.go

@@ -9,6 +9,8 @@ import "github.com/a-h/templ"
 import templruntime "github.com/a-h/templ/runtime"
 
 import "fmt"
+import "strconv"
+import "strings"
 
 // CalendarSummary is one calendar (own or shared) shown in the combined
 // month view's legend.
@@ -121,7 +123,7 @@ func MonthView(username string, data MonthViewData) templ.Component {
 			var templ_7745c5c3_Var3 templ.SafeURL
 			templ_7745c5c3_Var3, templ_7745c5c3_Err = templ.JoinURLErrs(templ.URL(data.PrevMonthURL))
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 81, Col: 42}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 83, Col: 42}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var3))
 			if templ_7745c5c3_Err != nil {
@@ -134,7 +136,7 @@ func MonthView(username string, data MonthViewData) templ.Component {
 			var templ_7745c5c3_Var4 templ.SafeURL
 			templ_7745c5c3_Var4, templ_7745c5c3_Err = templ.JoinURLErrs(templ.URL(data.TodayURL))
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 82, Col: 38}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 84, Col: 38}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var4))
 			if templ_7745c5c3_Err != nil {
@@ -147,7 +149,7 @@ func MonthView(username string, data MonthViewData) templ.Component {
 			var templ_7745c5c3_Var5 templ.SafeURL
 			templ_7745c5c3_Var5, templ_7745c5c3_Err = templ.JoinURLErrs(templ.URL(data.NextMonthURL))
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 83, Col: 42}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 85, Col: 42}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var5))
 			if templ_7745c5c3_Err != nil {
@@ -160,7 +162,7 @@ func MonthView(username string, data MonthViewData) templ.Component {
 			var templ_7745c5c3_Var6 string
 			templ_7745c5c3_Var6, templ_7745c5c3_Err = templ.JoinStringErrs(data.MonthLabel)
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 84, Col: 60}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 86, Col: 60}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var6))
 			if templ_7745c5c3_Err != nil {
@@ -198,7 +200,7 @@ func MonthView(username string, data MonthViewData) templ.Component {
 					var templ_7745c5c3_Var7 string
 					templ_7745c5c3_Var7, templ_7745c5c3_Err = templ.JoinStringErrs(wd)
 					if templ_7745c5c3_Err != nil {
-						return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 102, Col: 91}
+						return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 104, Col: 91}
 					}
 					_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var7))
 					if templ_7745c5c3_Err != nil {
@@ -263,14 +265,14 @@ func calendarLegendRow(c CalendarSummary) templ.Component {
 			templ_7745c5c3_Var8 = templ.NopComponent
 		}
 		ctx = templ.ClearChildren(ctx)
-		templ_7745c5c3_Err = templruntime.WriteString(templ_7745c5c3_Buffer, 14, "<div class=\"px-4 py-3 flex items-center gap-3 text-sm flex-wrap\"><span class=\"w-3 h-3 rounded-full shrink-0\" style=\"")
+		templ_7745c5c3_Err = templruntime.WriteString(templ_7745c5c3_Buffer, 14, "<div class=\"px-4 py-3 flex items-center gap-3 text-sm flex-wrap\"><span class=\"w-3 h-3 rounded-full shrink-0 ring-1 ring-inset ring-black/10\" style=\"")
 		if templ_7745c5c3_Err != nil {
 			return templ_7745c5c3_Err
 		}
 		var templ_7745c5c3_Var9 string
 		templ_7745c5c3_Var9, templ_7745c5c3_Err = templruntime.SanitizeStyleAttributeValues("background-color: " + colorOrDefault(c.Color))
 		if templ_7745c5c3_Err != nil {
-			return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 122, Col: 100}
+			return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 124, Col: 132}
 		}
 		_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var9))
 		if templ_7745c5c3_Err != nil {
@@ -283,7 +285,7 @@ func calendarLegendRow(c CalendarSummary) templ.Component {
 		var templ_7745c5c3_Var10 string
 		templ_7745c5c3_Var10, templ_7745c5c3_Err = templ.JoinStringErrs(c.Name)
 		if templ_7745c5c3_Err != nil {
-			return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 123, Col: 36}
+			return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 125, Col: 36}
 		}
 		_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var10))
 		if templ_7745c5c3_Err != nil {
@@ -301,7 +303,7 @@ func calendarLegendRow(c CalendarSummary) templ.Component {
 			var templ_7745c5c3_Var11 string
 			templ_7745c5c3_Var11, templ_7745c5c3_Err = templ.JoinStringErrs(c.Owner)
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 125, Col: 58}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 127, Col: 58}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var11))
 			if templ_7745c5c3_Err != nil {
@@ -330,7 +332,7 @@ func calendarLegendRow(c CalendarSummary) templ.Component {
 			var templ_7745c5c3_Var12 templ.SafeURL
 			templ_7745c5c3_Var12, templ_7745c5c3_Err = templ.JoinURLErrs(templ.URL("/web/calendar/" + c.Ref + "/export"))
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 132, Col: 60}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 134, Col: 60}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var12))
 			if templ_7745c5c3_Err != nil {
@@ -349,7 +351,7 @@ func calendarLegendRow(c CalendarSummary) templ.Component {
 			var templ_7745c5c3_Var13 templ.SafeURL
 			templ_7745c5c3_Var13, templ_7745c5c3_Err = templ.JoinURLErrs(templ.URL("/web/calendar/" + c.Ref + "/import"))
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 135, Col: 79}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 137, Col: 79}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var13))
 			if templ_7745c5c3_Err != nil {
@@ -423,7 +425,7 @@ func monthDayCell(day MonthDay) templ.Component {
 		var templ_7745c5c3_Var18 templ.SafeURL
 		templ_7745c5c3_Var18, templ_7745c5c3_Err = templ.JoinURLErrs(templ.URL("/web/calendar/new?date=" + day.Date))
 		if templ_7745c5c3_Err != nil {
-			return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 147, Col: 58}
+			return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 149, Col: 58}
 		}
 		_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var18))
 		if templ_7745c5c3_Err != nil {
@@ -449,7 +451,7 @@ func monthDayCell(day MonthDay) templ.Component {
 		var templ_7745c5c3_Var20 string
 		templ_7745c5c3_Var20, templ_7745c5c3_Err = templ.JoinStringErrs(fmt.Sprint(day.Day))
 		if templ_7745c5c3_Err != nil {
-			return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 151, Col: 25}
+			return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 153, Col: 25}
 		}
 		_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var20))
 		if templ_7745c5c3_Err != nil {
@@ -467,7 +469,7 @@ func monthDayCell(day MonthDay) templ.Component {
 			var templ_7745c5c3_Var21 templ.SafeURL
 			templ_7745c5c3_Var21, templ_7745c5c3_Err = templ.JoinURLErrs(templ.URL(eventLinkURL(ev)))
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 156, Col: 38}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 158, Col: 38}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var21))
 			if templ_7745c5c3_Err != nil {
@@ -478,9 +480,9 @@ func monthDayCell(day MonthDay) templ.Component {
 				return templ_7745c5c3_Err
 			}
 			var templ_7745c5c3_Var22 string
-			templ_7745c5c3_Var22, templ_7745c5c3_Err = templruntime.SanitizeStyleAttributeValues("background-color: " + colorOrDefault(ev.Color) + "22; color: " + colorOrDefault(ev.Color))
+			templ_7745c5c3_Var22, templ_7745c5c3_Err = templruntime.SanitizeStyleAttributeValues("background-color: " + colorOrDefault(ev.Color) + "22; color: " + eventTextColor(ev.Color))
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 158, Col: 102}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 160, Col: 102}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var22))
 			if templ_7745c5c3_Err != nil {
@@ -493,20 +495,20 @@ func monthDayCell(day MonthDay) templ.Component {
 			var templ_7745c5c3_Var23 string
 			templ_7745c5c3_Var23, templ_7745c5c3_Err = templ.ResolveAttributeValue(ev.Summary)
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 159, Col: 22}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 161, Col: 22}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ_7745c5c3_Var23)
 			if templ_7745c5c3_Err != nil {
 				return templ_7745c5c3_Err
 			}
-			templ_7745c5c3_Err = templruntime.WriteString(templ_7745c5c3_Buffer, 35, "\"><span class=\"inline-block w-1.5 h-1.5 rounded-full mr-1\" style=\"")
+			templ_7745c5c3_Err = templruntime.WriteString(templ_7745c5c3_Buffer, 35, "\"><span class=\"inline-block w-1.5 h-1.5 rounded-full mr-1 ring-1 ring-inset ring-black/10\" style=\"")
 			if templ_7745c5c3_Err != nil {
 				return templ_7745c5c3_Err
 			}
 			var templ_7745c5c3_Var24 string
-			templ_7745c5c3_Var24, templ_7745c5c3_Err = templruntime.SanitizeStyleAttributeValues("background-color: " + colorOrDefault(ev.Color))
+			templ_7745c5c3_Var24, templ_7745c5c3_Err = templruntime.SanitizeStyleAttributeValues("background-color: " + eventTextColor(ev.Color))
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 161, Col: 116}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 163, Col: 148}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var24))
 			if templ_7745c5c3_Err != nil {
@@ -524,7 +526,7 @@ func monthDayCell(day MonthDay) templ.Component {
 				var templ_7745c5c3_Var25 string
 				templ_7745c5c3_Var25, templ_7745c5c3_Err = templ.JoinStringErrs(ev.TimeText)
 				if templ_7745c5c3_Err != nil {
-					return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 163, Col: 44}
+					return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 165, Col: 44}
 				}
 				_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var25))
 				if templ_7745c5c3_Err != nil {
@@ -538,7 +540,7 @@ func monthDayCell(day MonthDay) templ.Component {
 			var templ_7745c5c3_Var26 string
 			templ_7745c5c3_Var26, templ_7745c5c3_Err = templ.JoinStringErrs(" " + ev.Summary)
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 165, Col: 22}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 167, Col: 22}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var26))
 			if templ_7745c5c3_Err != nil {
@@ -564,6 +566,55 @@ func eventLinkURL(ev EventSummary) string {
 	return "/web/calendar/" + ev.CalRef + "/" + ev.ID + "/edit"
 }
 
+// eventTextColor returns a color derived from hex, darkened if needed so
+// it stays legible as text on monthDayCell's very light (~13% opacity)
+// tinted event background. Without this, a light calendar color like
+// white or pale yellow renders its own event text as invisible or
+// near-invisible, since the same color is used for both the tint and the
+// text. Colors that are already dark enough are returned unchanged.
+func eventTextColor(hex string) string {
+	c := colorOrDefault(hex)
+	r, g, b, ok := parseHexColor(c)
+	if !ok {
+		return c
+	}
+	// Perceived luminance (ITU-R BT.601).
+	luminance := 0.299*float64(r) + 0.587*float64(g) + 0.114*float64(b)
+	const maxReadableLuminance = 170
+	if luminance <= maxReadableLuminance {
+		return c
+	}
+	// Scale each channel down so the color darkens towards black while
+	// keeping its hue, ending up comfortably below the threshold.
+	scale := maxReadableLuminance / luminance * 0.75
+	return fmt.Sprintf("#%02x%02x%02x", clampByte(float64(r)*scale), clampByte(float64(g)*scale), clampByte(float64(b)*scale))
+}
+
+// parseHexColor parses a "#rrggbb" string into its red/green/blue
+// components. ok is false for anything else (including 3-digit shorthand
+// hex, which colorOrDefault/hexColorRe never produce).
+func parseHexColor(s string) (r, g, b int, ok bool) {
+	s = strings.TrimPrefix(s, "#")
+	if len(s) != 6 {
+		return 0, 0, 0, false
+	}
+	v, err := strconv.ParseInt(s, 16, 32)
+	if err != nil {
+		return 0, 0, 0, false
+	}
+	return int(v >> 16 & 0xff), int(v >> 8 & 0xff), int(v & 0xff), true
+}
+
+func clampByte(v float64) int {
+	if v < 0 {
+		return 0
+	}
+	if v > 255 {
+		return 255
+	}
+	return int(v)
+}
+
 func EventForm(username string, data EventFormData, errMsg string) templ.Component {
 	return templruntime.GeneratedTemplate(func(templ_7745c5c3_Input templruntime.GeneratedComponentInput) (templ_7745c5c3_Err error) {
 		templ_7745c5c3_W, ctx := templ_7745c5c3_Input.Writer, templ_7745c5c3_Input.Context
@@ -624,7 +675,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 				var templ_7745c5c3_Var29 string
 				templ_7745c5c3_Var29, templ_7745c5c3_Err = templ.JoinStringErrs(errMsg)
 				if templ_7745c5c3_Err != nil {
-					return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 191, Col: 98}
+					return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 242, Col: 98}
 				}
 				_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var29))
 				if templ_7745c5c3_Err != nil {
@@ -652,7 +703,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 			var templ_7745c5c3_Var30 templ.SafeURL
 			templ_7745c5c3_Var30, templ_7745c5c3_Err = templ.JoinURLErrs(eventFormAction(data))
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 200, Col: 33}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 251, Col: 33}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var30))
 			if templ_7745c5c3_Err != nil {
@@ -685,7 +736,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 					var templ_7745c5c3_Var31 string
 					templ_7745c5c3_Var31, templ_7745c5c3_Err = templ.ResolveAttributeValue(c.Ref)
 					if templ_7745c5c3_Err != nil {
-						return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 209, Col: 28}
+						return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 260, Col: 28}
 					}
 					_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ_7745c5c3_Var31)
 					if templ_7745c5c3_Err != nil {
@@ -708,7 +759,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 					var templ_7745c5c3_Var32 string
 					templ_7745c5c3_Var32, templ_7745c5c3_Err = templ.JoinStringErrs(c.Label)
 					if templ_7745c5c3_Err != nil {
-						return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 209, Col: 75}
+						return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 260, Col: 75}
 					}
 					_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var32))
 					if templ_7745c5c3_Err != nil {
@@ -731,7 +782,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 				var templ_7745c5c3_Var33 string
 				templ_7745c5c3_Var33, templ_7745c5c3_Err = templ.JoinStringErrs(data.CalendarLabel)
 				if templ_7745c5c3_Err != nil {
-					return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 213, Col: 63}
+					return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 264, Col: 63}
 				}
 				_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var33))
 				if templ_7745c5c3_Err != nil {
@@ -749,7 +800,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 			var templ_7745c5c3_Var34 string
 			templ_7745c5c3_Var34, templ_7745c5c3_Err = templ.ResolveAttributeValue(data.Summary)
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 219, Col: 67}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 270, Col: 67}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ_7745c5c3_Var34)
 			if templ_7745c5c3_Err != nil {
@@ -772,7 +823,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 			var templ_7745c5c3_Var35 string
 			templ_7745c5c3_Var35, templ_7745c5c3_Err = templ.ResolveAttributeValue(data.StartDate)
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 231, Col: 73}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 282, Col: 73}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ_7745c5c3_Var35)
 			if templ_7745c5c3_Err != nil {
@@ -807,7 +858,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 			var templ_7745c5c3_Var38 string
 			templ_7745c5c3_Var38, templ_7745c5c3_Err = templ.ResolveAttributeValue(data.StartTime)
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 236, Col: 64}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 287, Col: 64}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ_7745c5c3_Var38)
 			if templ_7745c5c3_Err != nil {
@@ -820,7 +871,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 			var templ_7745c5c3_Var39 string
 			templ_7745c5c3_Var39, templ_7745c5c3_Err = templ.ResolveAttributeValue(data.EndDate)
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 241, Col: 69}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 292, Col: 69}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ_7745c5c3_Var39)
 			if templ_7745c5c3_Err != nil {
@@ -855,7 +906,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 			var templ_7745c5c3_Var42 string
 			templ_7745c5c3_Var42, templ_7745c5c3_Err = templ.ResolveAttributeValue(data.EndTime)
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 246, Col: 60}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 297, Col: 60}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ_7745c5c3_Var42)
 			if templ_7745c5c3_Err != nil {
@@ -868,7 +919,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 			var templ_7745c5c3_Var43 string
 			templ_7745c5c3_Var43, templ_7745c5c3_Err = templ.ResolveAttributeValue(data.Location)
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 253, Col: 60}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 304, Col: 60}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ_7745c5c3_Var43)
 			if templ_7745c5c3_Err != nil {
@@ -881,7 +932,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 			var templ_7745c5c3_Var44 string
 			templ_7745c5c3_Var44, templ_7745c5c3_Err = templ.JoinStringErrs(data.Description)
 			if templ_7745c5c3_Err != nil {
-				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 259, Col: 103}
+				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 310, Col: 103}
 			}
 			_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var44))
 			if templ_7745c5c3_Err != nil {
@@ -905,7 +956,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 				var templ_7745c5c3_Var45 templ.SafeURL
 				templ_7745c5c3_Var45, templ_7745c5c3_Err = templ.JoinURLErrs(templ.URL("/web/calendar/" + data.CalRef + "/" + data.ID + "/delete"))
 				if templ_7745c5c3_Err != nil {
-					return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 270, Col: 103}
+					return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 321, Col: 103}
 				}
 				_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var45))
 				if templ_7745c5c3_Err != nil {
@@ -924,7 +975,7 @@ func EventForm(username string, data EventFormData, errMsg string) templ.Compone
 				var templ_7745c5c3_Var46 templ.SafeURL
 				templ_7745c5c3_Var46, templ_7745c5c3_Err = templ.JoinURLErrs(templ.URL("/web/calendar/" + data.CalRef + "/" + data.ID + "/export"))
 				if templ_7745c5c3_Err != nil {
-					return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 275, Col: 84}
+					return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/web/templates/calendar.templ`, Line: 326, Col: 84}
 				}
 				_, templ_7745c5c3_Err = templ_7745c5c3_Buffer.WriteString(templ.EscapeString(templ_7745c5c3_Var46))
 				if templ_7745c5c3_Err != nil {

internal/web/templates/calendar_test.go

@@ -0,0 +1,43 @@
+package templates
+
+import "testing"
+
+// TestEventTextColorKeepsReadableColorsUnchanged covers the reported bug:
+// picking white (or any other very light color) for a calendar made its
+// events unreadable in the month view, since monthDayCell used the same
+// color for both the (barely tinted) background and the text. Light
+// colors must be darkened for text use; colors that were already fine
+// must render exactly as chosen.
+func TestEventTextColorKeepsReadableColorsUnchanged(t *testing.T) {
+	for _, c := range []string{"#3b82f6", "#ec4899", "#10b981", "#000000"} {
+		if got := eventTextColor(c); got != c {
+			t.Errorf("eventTextColor(%s) = %s, want unchanged", c, got)
+		}
+	}
+}
+
+func TestEventTextColorDarkensLightColors(t *testing.T) {
+	for _, c := range []string{"#ffffff", "#ffff00", "#f0f0f0", "#fefefe"} {
+		got := eventTextColor(c)
+		if got == c {
+			t.Errorf("eventTextColor(%s) = %s, want darkened for readability", c, got)
+		}
+		r, g, b, ok := parseHexColor(got)
+		if !ok {
+			t.Fatalf("eventTextColor(%s) returned unparseable color %s", c, got)
+		}
+		luminance := 0.299*float64(r) + 0.587*float64(g) + 0.114*float64(b)
+		if luminance > 170 {
+			t.Errorf("eventTextColor(%s) = %s still too light (luminance %.1f)", c, got, luminance)
+		}
+	}
+}
+
+func TestEventTextColorFallsBackForInvalidInput(t *testing.T) {
+	if got := eventTextColor(""); got != colorOrDefault("") {
+		t.Errorf("eventTextColor(\"\") = %s, want the same default colorOrDefault returns", got)
+	}
+	if got := eventTextColor("not-a-color"); got != "not-a-color" {
+		t.Errorf("eventTextColor(unparseable) = %s, want passed through unchanged", got)
+	}
+}