Fix Sphere v1 Font#drawZoomedText()

The font's alpha channel was lost due to not setting the blend mode
properly before rendering text.  Honestly the way this is implemented is
pretty inefficient, but I couldn't come up with a better way to do it.
Probably not worth the trouble at this point since Sphere v1 is
deprecated anyway.

CHANGELOG.md

@@ -4,8 +4,9 @@ miniSphere Changelog
 vX.X.X - TBD
 ------------
 
-* Fixes a long-standing bug in the RFN font loader that caused RFNv1 fonts to
-  be rendered without transparency.
+* Fixes a bug where Sphere v1 `drawZoomedText()` ignores non-opaque pixels.
+* Fixes a bug in the RFN font loader where RFNv1 (grayscale) fonts are loaded
+  without an alpha channel.
 
 
 v4.5.9 - March 31, 2017

src/minisphere/vanilla.c

@@ -3084,10 +3084,12 @@ js_Font_drawZoomedText(duk_context* ctx)
 	if (!screen_is_skipframe(g_screen)) {
 		text_w = font_get_width(font, text);
 		text_h = font_height(font);
+		apply_blend_mode(BLEND_REPLACE);
 		bitmap = al_create_bitmap(text_w, text_h);
 		al_set_target_bitmap(bitmap);
 		font_draw_text(font, mask, 0, 0, TEXT_ALIGN_LEFT, text);
 		al_set_target_backbuffer(screen_display(g_screen));
+		reset_blender();
 		al_draw_scaled_bitmap(bitmap, 0, 0, text_w, text_h, x, y, text_w * scale, text_h * scale, 0x0);
 		al_destroy_bitmap(bitmap);
 	}