Move swaybg background rendering into common/

swaylock will use it too

common/background-image.c

@@ -0,0 +1,100 @@
+#include <assert.h>
+#include <stdbool.h>
+#include <wlr/util/log.h>
+#include "background-image.h"
+#include "cairo.h"
+
+cairo_surface_t *load_background_image(const char *path) {
+	cairo_surface_t *image;
+#ifdef HAVE_GDK_PIXBUF
+	GError *err = NULL;
+	GdkPixbuf *pixbuf = gdk_pixbuf_new_from_file(path, &err);
+	if (!pixbuf) {
+		wlr_log(L_ERROR, "Failed to load background image.");
+		return false;
+	}
+	image = gdk_cairo_image_surface_create_from_pixbuf(pixbuf);
+	g_object_unref(pixbuf);
+#else
+	image = cairo_image_surface_create_from_png(path);
+#endif //HAVE_GDK_PIXBUF
+	if (!image) {
+		wlr_log(L_ERROR, "Failed to read background image.");
+		return NULL;
+	}
+	if (cairo_surface_status(image) != CAIRO_STATUS_SUCCESS) {
+		wlr_log(L_ERROR, "Failed to read background image: %s."
+#ifndef HAVE_GDK_PIXBUF
+				"\nSway was compiled without gdk_pixbuf support, so only"
+				"\nPNG images can be loaded. This is the likely cause."
+#endif //HAVE_GDK_PIXBUF
+				, cairo_status_to_string(cairo_surface_status(image)));
+		return NULL;
+	}
+	return image;
+}
+
+void render_background_image(cairo_t *cairo, cairo_surface_t *image,
+		enum background_mode mode, int buffer_width, int buffer_height,
+		int buffer_scale) {
+	double width = cairo_image_surface_get_width(image);
+	double height = cairo_image_surface_get_height(image);
+
+	switch (mode) {
+	case BACKGROUND_MODE_STRETCH:
+		cairo_scale(cairo,
+				(double)buffer_width / width,
+				(double)buffer_height / height);
+		cairo_set_source_surface(cairo, image, 0, 0);
+		break;
+	case BACKGROUND_MODE_FILL: {
+		double window_ratio = (double)buffer_width / buffer_height;
+		double bg_ratio = width / height;
+
+		if (window_ratio > bg_ratio) {
+			double scale = (double)buffer_width / width;
+			cairo_scale(cairo, scale, scale);
+			cairo_set_source_surface(cairo, image,
+					0, (double)buffer_height / 2 / scale - height / 2);
+		} else {
+			double scale = (double)buffer_height / height;
+			cairo_scale(cairo, scale, scale);
+			cairo_set_source_surface(cairo, image,
+					(double)buffer_width / 2 / scale - width / 2, 0);
+		}
+		break;
+	}
+	case BACKGROUND_MODE_FIT: {
+		double window_ratio = (double)buffer_width / buffer_height;
+		double bg_ratio = width / height;
+
+		if (window_ratio > bg_ratio) {
+			double scale = (double)buffer_height / height;
+			cairo_scale(cairo, scale, scale);
+			cairo_set_source_surface(cairo, image,
+					(double)buffer_width / 2 / scale - width / 2, 0);
+		} else {
+			double scale = (double)buffer_width / width;
+			cairo_scale(cairo, scale, scale);
+			cairo_set_source_surface(cairo, image,
+					0, (double)buffer_height / 2 / scale - height / 2);
+		}
+		break;
+	}
+	case BACKGROUND_MODE_CENTER:
+		cairo_set_source_surface(cairo, image,
+				(double)buffer_width / 2 - width / 2,
+				(double)buffer_height / 2 - height / 2);
+		break;
+	case BACKGROUND_MODE_TILE: {
+		cairo_pattern_t *pattern = cairo_pattern_create_for_surface(image);
+		cairo_pattern_set_extend(pattern, CAIRO_EXTEND_REPEAT);
+		cairo_set_source(cairo, pattern);
+		break;
+	}
+	case BACKGROUND_MODE_SOLID_COLOR:
+		assert(0);
+		break;
+	}
+	cairo_paint(cairo);
+}

common/meson.build

@@ -1,17 +1,7 @@
-deps = [
-	cairo,
-	pango,
-	pangocairo,
-	wlroots
-]
-
-if gdk_pixbuf.found()
-	deps += [gdk_pixbuf]
-endif
-
 lib_sway_common = static_library(
 	'sway-common',
 	files(
+		'background-image.c',
 		'cairo.c',
 		'ipc-client.c',
 		'log.c',
@@ -21,6 +11,12 @@ lib_sway_common = static_library(
 		'stringop.c',
 		'util.c'
 	),
-	dependencies: deps,
+	dependencies: [
+		cairo,
+		gdk_pixbuf,
+		pango,
+		pangocairo,
+		wlroots
+	],
 	include_directories: sway_inc
 )