Fix #8731: Always use a 32bpp blitter if font anti-aliasing is enabled.

src/fontcache.cpp

@@ -279,10 +279,10 @@ void TrueTypeFontCache::SetGlyphPtr(GlyphID key, const GlyphEntry *glyph, bool d
 
 
 /* Check if a glyph should be rendered with anti-aliasing. */
-static bool GetFontAAState(FontSize size)
+static bool GetFontAAState(FontSize size, bool check_blitter = true)
 {
 	/* AA is only supported for 32 bpp */
-	if (BlitterFactory::GetCurrentBlitter()->GetScreenDepth() != 32) return false;
+	if (check_blitter && BlitterFactory::GetCurrentBlitter()->GetScreenDepth() != 32) return false;
 
 	switch (size) {
 		default: NOT_REACHED();
@@ -716,6 +716,19 @@ void UninitFreeType()
 #endif /* WITH_FREETYPE */
 }
 
+/**
+ * Should any of the active fonts be anti-aliased?
+ * @return True if any of the loaded fonts want anti-aliased drawing.
+ */
+bool HasAntialiasedFonts()
+{
+	for (FontSize fs = FS_BEGIN; fs < FS_END; fs++) {
+		if (!FontCache::Get(fs)->IsBuiltInFont() && GetFontAAState(fs, false)) return true;
+	}
+
+	return false;
+}
+
 #if !defined(_WIN32) && !defined(__APPLE__) && !defined(WITH_FONTCONFIG) && !defined(WITH_COCOA)
 
 #ifdef WITH_FREETYPE

src/fontcache.h

@@ -233,5 +233,6 @@ extern FreeTypeSettings _freetype;
 
 void InitFreeType(bool monospace);
 void UninitFreeType();
+bool HasAntialiasedFonts();
 
 #endif /* FONTCACHE_H */

src/gfxinit.cpp

@@ -268,6 +268,8 @@ static bool SwitchNewGRFBlitter()
 		if (c->status == GCS_DISABLED || c->status == GCS_NOT_FOUND || HasBit(c->flags, GCF_INIT_ONLY)) continue;
 		if (c->palette & GRFP_BLT_32BPP) depth_wanted_by_grf = 32;
 	}
+	/* We need a 32bpp blitter for font anti-alias. */
+	if (HasAntialiasedFonts()) depth_wanted_by_grf = 32;
 
 	/* Search the best blitter. */
 	static const struct {

src/settings_gui.cpp

@@ -433,6 +433,7 @@ struct GameOptionsWindow : Window {
 				CheckForMissingGlyphs();
 				ClearAllCachedNames();
 				UpdateAllVirtCoords();
+				CheckBlitter();
 				ReInitAllWindows();
 				break;