fix(renderer): Small gaps when rendering emojis (#2802)

If any rendered text uses a non-integer number of pixels (often emojis),
rendering of subsequent text blocks will start between pixels which
results in small gaps in the background and over/underline colors caused
by cairo only rendering at fractional-intensity in the beginning and end
pixel.

Simply rounding up text width can solve this.

Fixes #2785

CHANGELOG.md

@@ -34,6 +34,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 - Waiting for double click interval on modules that don't have a double click action ([`#2663`](https://github.com/polybar/polybar/issues/2663), [`#2695`](https://github.com/polybar/polybar/pull/2695))
+- renderer: Small gaps when rendering emojis ([`#2785`](https://github.com/polybar/polybar/issues/2785), [`#2802`](https://github.com/polybar/polybar/pull/2802))
 - config:
   - Error reporting for deprecated config values ([`#2724`](https://github.com/polybar/polybar/issues/2724))
   - Also monitor include-files for changes when --reload is set ([`#675`](https://github.com/polybar/polybar/issues/675), [`#2759`](https://github.com/polybar/polybar/pull/2759))

include/cairo/context.hpp

@@ -196,6 +196,12 @@ namespace cairo {
           cairo_text_extents_t extents;
           f->textwidth(subset, &extents);
 
+          /*
+           * Make sure we don't advance partial pixels, this can cause problems
+           * later when cairo renders background colors over half-pixels.
+           */
+          extents.x_advance = std::ceil(extents.x_advance);
+
           // Draw the background
           if (t.bg_rect.h != 0.0) {
             save();