Apply the theme from PageSettings in JS, before the first paint

wwwroot/js/theme.js now picks the theme. It sets data-theme (neo-light or
neo-dark, or none when the OS decides) and the hue and chroma variables on
<html>, using the same flag precedence as the old CascadingState branches. It
also keeps <meta name="theme-color"> in sync. Because it runs in <head> from the
settings saved in localStorage, a reload no longer flashes the default palette
before Blazor boots. With system theming it also follows the OS when the colour
scheme changes.

CascadingState loses its ~200 lines of generated <style> and <Meta> tags. It now
calls AppStatusService.ApplyTheme on load and whenever the settings change. The
--fa-* icon colour variables are gone; nothing read them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw
This commit is contained in:
thepraandClaude Opus 5.5 committed 2026-10-03 11:29:31 +02:00
1 parent 5b5fd62233
commit 8e03d12a3e
4 files changed
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+4 -202
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@@ -1,205 +1,4 @@
@if (PublicCacheData != null)
{
if (PublicCacheData.PageSettings.ThemeIsDarkMode)
{
<Meta Content="@($"hsl({PublicCacheData.PageSettings.DarkThemeIndexColour},16%,12%)")" Name="theme-color"/>
<Meta Content="@($"hsl({PublicCacheData.PageSettings.DarkThemeIndexColour},16%,12%)")" Name="background-color"/>
}
else
{
<Meta Content="@($"hsl({PublicCacheData.PageSettings.LightThemeIndexColour},84%,88%)")" Name="theme-color"/>
<Meta Content="@($"hsl({PublicCacheData.PageSettings.LightThemeIndexColour},84%,88%)")" Name="background-color"/>
}
}
<HeadContent>
<style>
@if (PublicCacheData != null)
{
var iconsColour = PublicCacheData.PageSettings.IconsThemeIndexColour is >= 0 and <= 359 ?
$"--fa-primary-color: hsl({PublicCacheData.PageSettings.IconsThemeIndexColour},84%,26.4%);--fa-secondary-color: hsl({PublicCacheData.PageSettings.IconsThemeIndexColour},84%,66%);" :
PublicCacheData.PageSettings.IconsThemeIndexColour is -2 ?
$"--fa-primary-color: hsl(0,0%,1%);--fa-secondary-color: hsl(0,0%,40%);" :
$"--fa-primary-color: hsl(0,0%,60%);--fa-secondary-color: hsl(0,0%,99%);";
@if (PublicCacheData.PageSettings.PreferSystemTheming)
{
if (PublicCacheData.PageSettings.ThemeIsDarkGray || PublicCacheData.PageSettings.ThemeIsLightGray)
{
@($@"@media screen and (prefers-color-scheme: light) {{
:root {{
--colour-index: 0;
--background: hsl(0,0%,88%);
--text-color: hsl(0,0%,26.4%);
--placeholder-text-color: hsla(0,0%,26.4%,.4);
--primary-color: hsl(0,0%,88%);
--primary-color-light: hsl(0,0%,100%);
--primary-color-dark: hsl(0,0%,66%);
--primary-gradiend-light: hsl(0,0%,92%);
--primary-gradiend-dark: hsl(0,0%,84%);
--primary-gradiend-lighter: hsl(0,0%,96%);
--primary-gradiend-darker: hsl(0,0%,80%);
--light-shadow: hsla(0,0%,100%, .5);
--dark-shadow: hsla(0,0%,66%, .5);
--danger-gradiend-light: hsl(0,0%,92%);
--danger-gradiend-dark: hsl(0,0%,84%);
{iconsColour}
}}
}}
@media screen and (prefers-color-scheme: dark) {{
:root {{
--colour-index: 0;
--background: hsl(0,0%,12%);
--text-color: hsl(0,0%,73.6%);
--placeholder-text-color: hsla(0,0%,52.8%,.4);
--primary-color: hsl(0,0%,12%);
--primary-color-light: hsl(0,0%,100%);
--primary-color-dark: hsl(0,0%,33%);
--primary-gradiend-light: hsl(0,0%,16%);
--primary-gradiend-dark: hsl(0,0%,8%);
--primary-gradiend-lighter: hsl(0,0%,20%);
--primary-gradiend-darker: hsl(0,0%,4%);
--light-shadow: hsla(0,0%,66%,.1);
--dark-shadow: hsla(0,0%,1%,.5);
--danger-gradiend-light: hsl(0,16%,16%);
--danger-gradiend-dark: hsl(0,16%,8%);
{iconsColour}
}}
}}")
}
else
{
@($@"@media screen and (prefers-color-scheme: light) {{
:root {{
--colour-index: {PublicCacheData.PageSettings.LightThemeIndexColour};
--background: hsl(var(--colour-index,25),84%,88%);
--text-color: hsl(var(--colour-index,25),84%,26.4%);
--placeholder-text-color: hsla(var(--colour-index,25),84%,26.4%,.4);
--primary-color: hsl(var(--colour-index,25),84%,88%);
--primary-color-light: hsl(var(--colour-index,25),84%,100%);
--primary-color-dark: hsl(var(--colour-index,25),84%,66%);
--primary-gradiend-light: hsl(var(--colour-index,25),84%,92%);
--primary-gradiend-dark: hsl(var(--colour-index,25),84%,84%);
--primary-gradiend-lighter: hsl(var(--colour-index,25),84%,96%);
--primary-gradiend-darker: hsl(var(--colour-index,25),84%,80%);
--light-shadow: hsla(var(--colour-index,25),84%,100%, .5);
--dark-shadow: hsla(var(--colour-index,25),84%,66%, .5);
--danger-gradiend-light: hsl(0,84%,92%);
--danger-gradiend-dark: hsl(0,84%,84%);
{iconsColour}
}}
}}
@media screen and (prefers-color-scheme: dark) {{
:root {{
--colour-index: {PublicCacheData.PageSettings.DarkThemeIndexColour};
--background: hsl(var(--colour-index,215),16%,12%);
--text-color: hsl(var(--colour-index,215),16%,73.6%);
--placeholder-text-color: hsla(var(--colour-index,25),84%,26.4%,.4);
--primary-color: hsl(var(--colour-index,215),16%,12%);
--primary-color-light: hsl(var(--colour-index,215),84%,100%);
--primary-color-dark: hsl(var(--colour-index,215),16%,33%);
--primary-gradiend-light: hsl(var(--colour-index,215),16%,16%);
--primary-gradiend-dark: hsl(var(--colour-index,215),16%,8%);
--primary-gradiend-lighter: hsl(var(--colour-index,215),16%,20%);
--primary-gradiend-darker: hsl(var(--colour-index,215),16%,4%);
--light-shadow: hsla(var(--colour-index,215),84%,66%,.1);
--dark-shadow: hsla(var(--colour-index,215),16%,1%,.5);
--danger-gradiend-light: hsl(0,16%,16%);
--danger-gradiend-dark: hsl(0,16%,8%);
{iconsColour}
}}
}}")
}
}
else
{
if (PublicCacheData.PageSettings.ThemeIsDarkGray || PublicCacheData.PageSettings.ThemeIsLightGray)
{
if (PublicCacheData.PageSettings.ThemeIsDarkGray)
{
@($@":root{{--colour-index: 0;
--background: hsl(0,0%,12%);
--text-color: hsl(0,0%,73.6%);
--placeholder-text-color: hsla(0,0%,73.6%,.4);
--primary-color: hsl(0,0%,12%);
--primary-color-light: hsl(0,0%,100%);
--primary-color-dark: hsl(0,0%,33%);
--primary-gradiend-light: hsl(0,0%,16%);
--primary-gradiend-dark: hsl(0,0%,8%);
--primary-gradiend-lighter: hsl(0,0%,20%);
--primary-gradiend-darker: hsl(0,0%,4%);
--light-shadow: hsla(0,0%,66%,.1);
--dark-shadow: hsla(0,0%,1%,.5);
--danger-gradiend-light: hsl(0,16%,16%);
--danger-gradiend-dark: hsl(0,16%,8%);{iconsColour}}}")
}
else
{
@($@":root{{--colour-index: 0;
--background: hsl(0,0%,88%);
--text-color: hsl(0,0%,26.4%);
--placeholder-text-color: hsla(0,0%,26.4%,.4);
--primary-color: hsl(0,0%,88%);
--primary-color-light: hsl(0,0%,100%);
--primary-color-dark: hsl(0,0%,66%);
--primary-gradiend-light: hsl(0,0%,92%);
--primary-gradiend-dark: hsl(0,0%,84%);
--primary-gradiend-lighter: hsl(0,0%,96%);
--primary-gradiend-darker: hsl(0,0%,80%);
--light-shadow: hsla(0,0%,100%, .5);
--dark-shadow: hsla(0,0%,66%, .5);
--danger-gradiend-light: hsl(0,84%,92%);
--danger-gradiend-dark: hsl(0,84%,84%);{iconsColour}}}")
}
}
else
{
if (PublicCacheData.PageSettings.ThemeIsDarkMode)
{
@($@":root{{--colour-index: {PublicCacheData.PageSettings.DarkThemeIndexColour};
--background: hsl(var(--colour-index,215),16%,12%);
--text-color: hsl(var(--colour-index,215),16%,73.6%);
--placeholder-text-color: hsla(var(--colour-index,215),16%,73.6%,.4);
--primary-color: hsl(var(--colour-index,215),16%,12%);
--primary-color-light: hsl(var(--colour-index,215),84%,100%);
--primary-color-dark: hsl(var(--colour-index,215),16%,33%);
--primary-gradiend-light: hsl(var(--colour-index,215),16%,16%);
--primary-gradiend-dark: hsl(var(--colour-index,215),16%,8%);
--primary-gradiend-lighter: hsl(var(--colour-index,215),16%,20%);
--primary-gradiend-darker: hsl(var(--colour-index,215),16%,4%);
--light-shadow: hsla(var(--colour-index,215),84%,66%,.1);
--dark-shadow: hsla(var(--colour-index,215),16%,1%,.5);
--danger-gradiend-light: hsl(0,16%,16%);
--danger-gradiend-dark: hsl(0,16%,8%);{iconsColour}}}")
}
else
{
@($@":root{{--colour-index: {PublicCacheData.PageSettings.LightThemeIndexColour};
--background: hsl(var(--colour-index,25),84%,88%);
--text-color: hsl(var(--colour-index,25),84%,26.4%);
--placeholder-text-color: hsla(var(--colour-index,25),84%,26.4%,.4);
--primary-color: hsl(var(--colour-index,25),84%,88%);
--primary-color-light: hsl(var(--colour-index,25),84%,100%);
--primary-color-dark: hsl(var(--colour-index,25),84%,66%);
--primary-gradiend-light: hsl(var(--colour-index,25),84%,92%);
--primary-gradiend-dark: hsl(var(--colour-index,25),84%,84%);
--primary-gradiend-lighter: hsl(var(--colour-index,25),84%,96%);
--primary-gradiend-darker: hsl(var(--colour-index,25),84%,80%);
--light-shadow: hsla(var(--colour-index,25),84%,100%, .5);
--dark-shadow: hsla(var(--colour-index,25),84%,66%, .5);
--danger-gradiend-light: hsl(0,84%,92%);
--danger-gradiend-dark: hsl(0,84%,84%);{iconsColour}}}")
}
}
}
}
</style>
</HeadContent>
<CascadingValue IsFixed=false Value=this>
<CascadingValue IsFixed=false Value=this>
@ChildContent
</CascadingValue>
@@ -232,6 +31,8 @@
PublicCacheData = new();
await UpdatePublicCache(PublicCacheData);
}
else
Status.ApplyTheme(PublicCacheData.PageSettings);
User = new();
}
@@ -247,6 +48,7 @@
{
PublicCacheData = publicCacheData;
await Storage.SetItemAsync(nameof(PublicCacheData), PublicCacheData);
Status.ApplyTheme(PublicCacheData.PageSettings);
StateHasChanged();
}
catch (Exception ex)
+6 -1
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@@ -1,4 +1,6 @@
using Microsoft.JSInterop;
using decePubClient.Models;
using Microsoft.JSInterop;
namespace decePubClient.Services;
@@ -44,6 +46,9 @@ public class AppStatusService
JsSyncRuntime.InvokeVoid("reloadPage");
}
// wwwroot/js/theme.js
public void ApplyTheme(PageSettings pageSettings) => JsSyncRuntime.InvokeVoid("neoTheme.apply", pageSettings);
public bool IsMobileMedia() => JsSyncRuntime.Invoke<bool>("isMobileMedia");
public bool CanShare() => JsSyncRuntime.Invoke<bool>("canShareStuff");
+2
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@@ -8,6 +8,8 @@
<base href="/" />
<link href="vendor/ionicons.min.css" rel="stylesheet" />
<link href="css/app.css" rel="stylesheet" />
<meta name="theme-color" content="hsl(0 0% 88%)" />
<script src="js/theme.js"></script>
<link href="manifest.json" rel="manifest" />
<link rel="apple-touch-icon" sizes="512x512" href="imgs/icon-512.png" />
<link rel="apple-touch-icon" sizes="192x192" href="imgs/icon-192.png" />
+52
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@@ -0,0 +1,52 @@
// Applies PageSettings to the page. It picks the daisyUI theme from Styles/theme.css and sets the hue and chroma
// variables that theme derives every colour from. It loads in <head> right after css/app.css and applies the
// settings saved in localStorage before the first paint. Once Blazor runs, CascadingState calls neoTheme.apply
// through AppStatusService.ApplyTheme whenever the settings change.
(() => {
const root = document.documentElement
let current = null
// The same precedence the old CascadingState <style> block had:
// - System theming leaves data-theme off, so daisyUI's prefersdark rule decides.
// - Otherwise dark grey, then light grey, then dark mode, then light.
// - Either grey flag drops the chroma to 0.
const apply = (settings) => {
current = settings || {}
const system = current.preferSystemTheming ?? true
const darkGray = current.themeIsDarkGray ?? false
const lightGray = current.themeIsLightGray ?? true
const dark = current.themeIsDarkMode ?? false
const theme = system ? null : darkGray ? "neo-dark" : lightGray ? "neo-light" : dark ? "neo-dark" : "neo-light"
if (theme)
root.setAttribute("data-theme", theme)
else
root.removeAttribute("data-theme")
root.style.setProperty("--neo-hue-light", current.lightThemeIndexColour ?? 25)
root.style.setProperty("--neo-hue-dark", current.darkThemeIndexColour ?? 215)
root.style.setProperty("--neo-chroma", darkGray || lightGray ? 0 : 1)
// daisyUI paints the root with base-100, so its computed background is the resolved theme colour.
let meta = document.querySelector('meta[name="theme-color"]')
if (!meta) {
meta = document.createElement("meta")
meta.name = "theme-color"
document.head.appendChild(meta)
}
meta.content = getComputedStyle(root).backgroundColor
}
try {
const cache = JSON.parse(localStorage.getItem("PublicCacheData") || "null")
apply(cache && cache.pageSettings)
} catch (e) {
console.error("theme.js", e)
apply(null)
}
// With system theming the OS can switch between light and dark at any time.
window.matchMedia("(prefers-color-scheme: dark)").addEventListener("change", () => apply(current))
window.neoTheme = { apply }
})()