custom_theme/custom_theme.cpp

Your own CSS classes next to the library's, and switching palettes and font size at runtime.

Your own CSS classes next to the library's, and switching palettes and font size at runtime. Its classes are in custom_theme.css. Walkthrough: Custom theme.

// Custom theme: the app adds its own CSS file next to the library's styles,
// uses its classes by name, and switches between the dark and light palettes.
#include <gui_controls/gui_application.h>
 
#include <cstdio>
 
#include <string_view>
 
class ThemeApp : public tachyon::GUIApplication
{
public:
    tachyon::Result<void> Initialize(const InitializeOptions& options = {}) override
    {
        // The library's rules first, then the app's (relative paths are next to the palette).
        const std::string_view styleFiles[] = { "styles.css", TACHYON_EXAMPLE_DIR "/custom_theme.css" };
        SetStyleFiles(styleFiles);
        if (tachyon::Result<void> result = GUIApplication::Initialize(options); !result)
            return result;
        windowID = idManager.CreateStaticID();
        return {};
    }
 
    void OnGUI() override
    {
        // The scope ends the window when it leaves, open or not.
        auto window = Window(windowID, "Custom theme", tachyon::LayoutOverride{}.Size(400, 220));
        if (!window)
            return;
        BeginVertical(tachyon::LayoutOverride{}.FlexGrow(1));
 
        // Look the classes up every frame: a theme reload registers new styles.
        Text("My themed app", theme.GetStyle("banner"));
 
        BeginHorizontal();
        Button("Dark",  [this] { RequestReloadTheme("themes/dark.css",  GetGlobalFontScale()); });
        Button("Light", [this] { RequestReloadTheme("themes/light.css", GetGlobalFontScale()); });
        EndHorizontal();
 
        BeginHorizontal();
        Button("Smaller text", [this] { RequestReloadTheme(GetThemePath(), GetGlobalFontScale() * 0.9f); });
        Button("Larger text",  [this] { RequestReloadTheme(GetThemePath(), GetGlobalFontScale() * 1.1f); });
        EndHorizontal();
 
        Button("Careful!", [] {}, theme.GetStyle("warning-button"));
        EndVertical();
    }
 
private:
    tachyon::ID windowID = tachyon::ID::Invalid();
};
 
int main()
{
    ThemeApp app;
    tachyon::Result<void> result = app.Initialize();
    if (result)
        result = app.Run();
    app.Cleanup();
    if (!result)
    {
        std::fprintf(stderr, "%s\n", result.GetError().message.c_str());
        return 1;
    }
    return 0;
}