Revert "config: don't allow colors.flash-alpha to be 1.0"

This reverts commit 56d2c3e990.

CHANGELOG.md

@@ -80,9 +80,6 @@
 
 * Runtime changes to the app-id (OSC-176) now limits the app-id string
   to 2048 characters ([#1897][1897]).
-* `colors.flash-alpha` can no longer be set to 1.0 (i.e. fully
-  opaque). This fixes an issue where the window would be stuck in the
-  flash state.
 
 [1897]: https://codeberg.org/dnkl/foot/issues/1897
 

config.c

@@ -1445,8 +1445,8 @@ parse_section_colors(struct context *ctx)
         if (!value_to_float(ctx, &alpha))
             return false;
 
-        if (alpha < 0. || alpha >= 1.) {
+        if (alpha < 0. || alpha > 1.) {
-            LOG_CONTEXTUAL_ERR("not in range 0.0-0.999");
+            LOG_CONTEXTUAL_ERR("not in range 0.0-1.0");
             return false;
         }
 

render.c

@@ -1898,27 +1898,6 @@ render_overlay(struct terminal *term)
         break;
 
     case OVERLAY_FLASH:
-        /*
-         * A compositor will not send a frame callback for our main
-         * window if it is fully occluded (for example, by a fully
-         * opaque overlay...). This causes the overlay to stuck.
-         *
-         * For regular buffers, it _should_ be enough to *not* hint
-         * the compositor it's opaque. But at least some compositor
-         * special cases single-pixel buffers, and actually look at
-         * their pixel value.
-         *
-         * Thus, we have two options: implement frame callback
-         * handling for the overlay sub-surface, or ensure we don't
-         * use a fully opaque surface. Since no overlays are fully
-         * opaque by default, and the flash surface is the only one
-         * that can be configured to be opaque (colors.flash-alpha),
-         * and since adding frame callback handling adds a lot of
-         * boilerplate code... let's go with the simpler solution of
-         * not allowing colors.flash-alpha to be 1.0.
-         */
-        xassert(term->conf->colors.flash_alpha != 0xffff);
-
         color = color_hex_to_pixman_with_alpha(
                 term->conf->colors.flash,
                 term->conf->colors.flash_alpha);