Set default background color to black

This ensures that the background is always opaque.

This is a significant change; before, if no background color was
specified, images were drawn onto an initially transparent buffer,
leaving some of the content behind swaybg visible if the image was
alpha transparent or if the 'fit' or 'center' scaling modes were used
and the image aspect ratio did not match, or the image was not large
enough. As the purpose of a wallpaper/background program is to draw
the pixels behind all other interface items, this transparency is
neither a required nor a very useful behavior.

Sway version >= 1.9 by default clears frames with black, so this
change should have no visible impact. Users of other compositors
may need to adjust their images or specify the --color flag.

1 files changed, 11 insertions, 21 deletions

diff --git a/main.c b/main.c
index 1f51cf4..0f5e7ad 100644
--- a/main.c
+++ b/main.c
@@ -99,21 +99,22 @@ struct swaybg_output {
 // Create a wl_buffer with the specified dimensions and content
 static struct wl_buffer *draw_buffer(const struct swaybg_output *output,
 		cairo_surface_t *surface, uint32_t buffer_width, uint32_t buffer_height) {
+	uint32_t bg_color = output->config->color ? output->config->color : 0x000000ff;
+
 	if (buffer_width == 1 && buffer_height == 1 &&
 			output->config->mode == BACKGROUND_MODE_SOLID_COLOR &&
 			output->state->single_pixel_buffer_manager) {
 		// create and return single pixel buffer
-		uint8_t r8 = (output->config->color >> 24) & 0xFF;
-		uint8_t g8 = (output->config->color >> 16) & 0xFF;
-		uint8_t b8 = (output->config->color >> 8) & 0xFF;
-		uint8_t a8 = (output->config->color >> 0) & 0xFF;
+		uint8_t r8 = (bg_color >> 24) & 0xFF;
+		uint8_t g8 = (bg_color >> 16) & 0xFF;
+		uint8_t b8 = (bg_color >> 8) & 0xFF;
 		uint32_t f = 0xFFFFFFFF / 0xFF; // division result is an integer
 		uint32_t r32 = r8 * f;
 		uint32_t g32 = g8 * f;
 		uint32_t b32 = b8 * f;
-		uint32_t a32 = a8 * f;
 		return wp_single_pixel_buffer_manager_v1_create_u32_rgba_buffer(
-			output->state->single_pixel_buffer_manager, r32, g32, b32, a32);
+			output->state->single_pixel_buffer_manager,
+			r32, g32, b32, 0xFFFFFFFF);
 	}
 
 
@@ -124,23 +125,12 @@ static struct wl_buffer *draw_buffer(const struct swaybg_output *output,
 	}
 
 	cairo_t *cairo = buffer.cairo;
-	cairo_save(cairo);
-	cairo_set_operator(cairo, CAIRO_OPERATOR_CLEAR);
+	cairo_set_source_u32(cairo, bg_color);
 	cairo_paint(cairo);
-	cairo_restore(cairo);
-	if (output->config->mode == BACKGROUND_MODE_SOLID_COLOR) {
-		cairo_set_source_u32(cairo, output->config->color);
-		cairo_paint(cairo);
-	} else {
-		if (output->config->color) {
-			cairo_set_source_u32(cairo, output->config->color);
-			cairo_paint(cairo);
-		}
 
-		if (surface) {
-			render_background_image(cairo, surface,
-				output->config->mode, buffer_width, buffer_height);
-		}
+	if (surface) {
+		render_background_image(cairo, surface,
+			output->config->mode, buffer_width, buffer_height);
 	}
 
 	// return wl_buffer for caller to use and destroy