Add solid-color rendering to swaybg

2 files changed, 143 insertions, 5 deletions

diff --git a/common/cairo.c b/common/cairo.c
new file mode 100644
index 00000000..c6bd0da9
--- /dev/null
+++ b/common/cairo.c
@@ -0,0 +1,127 @@
+#include <stdint.h>
+#include <cairo/cairo.h>
+#include "cairo.h"
+#ifdef WITH_GDK_PIXBUF
+#include <gdk-pixbuf/gdk-pixbuf.h>
+#endif
+
+void cairo_set_source_u32(cairo_t *cairo, uint32_t color) {
+	cairo_set_source_rgba(cairo,
+			(color >> (3*8) & 0xFF) / 255.0,
+			(color >> (2*8) & 0xFF) / 255.0,
+			(color >> (1*8) & 0xFF) / 255.0,
+			(color >> (0*8) & 0xFF) / 255.0);
+}
+
+cairo_surface_t *cairo_image_surface_scale(cairo_surface_t *image,
+		int width, int height) {
+	int image_width = cairo_image_surface_get_width(image);
+	int image_height = cairo_image_surface_get_height(image);
+
+	cairo_surface_t *new =
+		cairo_image_surface_create(CAIRO_FORMAT_ARGB32, width, height);
+	cairo_t *cairo = cairo_create(new);
+	cairo_scale(cairo, (double)width / image_width,
+			(double)height / image_height);
+	cairo_set_source_surface(cairo, image, 0, 0);
+
+	cairo_paint(cairo);
+	cairo_destroy(cairo);
+	return new;
+}
+
+#ifdef WITH_GDK_PIXBUF
+cairo_surface_t* gdk_cairo_image_surface_create_from_pixbuf(const GdkPixbuf *gdkbuf) {
+	int chan = gdk_pixbuf_get_n_channels(gdkbuf);
+	if (chan < 3) {
+		return NULL;
+	}
+
+	const guint8* gdkpix = gdk_pixbuf_read_pixels(gdkbuf);
+	if (!gdkpix) {
+		return NULL;
+	}
+	gint w = gdk_pixbuf_get_width(gdkbuf);
+	gint h = gdk_pixbuf_get_height(gdkbuf);
+	int stride = gdk_pixbuf_get_rowstride(gdkbuf);
+
+	cairo_format_t fmt = (chan == 3) ? CAIRO_FORMAT_RGB24 : CAIRO_FORMAT_ARGB32;
+	cairo_surface_t * cs = cairo_image_surface_create (fmt, w, h);
+	cairo_surface_flush (cs);
+	if ( !cs || cairo_surface_status(cs) != CAIRO_STATUS_SUCCESS) {
+		return NULL;
+	}
+
+	int cstride = cairo_image_surface_get_stride(cs);
+	unsigned char * cpix = cairo_image_surface_get_data(cs);
+
+	if (chan == 3) {
+		int i;
+		for (i = h; i; --i) {
+			const guint8 *gp = gdkpix;
+			unsigned char *cp = cpix;
+			const guint8* end = gp + 3*w;
+			while (gp < end) {
+#if G_BYTE_ORDER == G_LITTLE_ENDIAN
+				cp[0] = gp[2];
+				cp[1] = gp[1];
+				cp[2] = gp[0];
+#else
+				cp[1] = gp[0];
+				cp[2] = gp[1];
+				cp[3] = gp[2];
+#endif
+				gp += 3;
+				cp += 4;
+			}
+			gdkpix += stride;
+			cpix += cstride;
+		}
+	} else {
+		/* premul-color = alpha/255 * color/255 * 255 = (alpha*color)/255
+		 * (z/255) = z/256 * 256/255     = z/256 (1 + 1/255)
+		 *         = z/256 + (z/256)/255 = (z + z/255)/256
+		 *         # recurse once
+		 *         = (z + (z + z/255)/256)/256
+		 *         = (z + z/256 + z/256/255) / 256
+		 *         # only use 16bit uint operations, loose some precision,
+		 *         # result is floored.
+		 *       ->  (z + z>>8)>>8
+		 *         # add 0x80/255 = 0.5 to convert floor to round
+		 *       =>  (z+0x80 + (z+0x80)>>8 ) >> 8
+		 * ------
+		 * tested as equal to lround(z/255.0) for uint z in [0..0xfe02]
+		 */
+#define PREMUL_ALPHA(x,a,b,z) \
+		G_STMT_START { z = a * b + 0x80; x = (z + (z >> 8)) >> 8; } \
+		G_STMT_END
+		int i;
+		for (i = h; i; --i) {
+			const guint8 *gp = gdkpix;
+			unsigned char *cp = cpix;
+			const guint8* end = gp + 4*w;
+			guint z1, z2, z3;
+			while (gp < end) {
+#if G_BYTE_ORDER == G_LITTLE_ENDIAN
+				PREMUL_ALPHA(cp[0], gp[2], gp[3], z1);
+				PREMUL_ALPHA(cp[1], gp[1], gp[3], z2);
+				PREMUL_ALPHA(cp[2], gp[0], gp[3], z3);
+				cp[3] = gp[3];
+#else
+				PREMUL_ALPHA(cp[1], gp[0], gp[3], z1);
+				PREMUL_ALPHA(cp[2], gp[1], gp[3], z2);
+				PREMUL_ALPHA(cp[3], gp[2], gp[3], z3);
+				cp[0] = gp[3];
+#endif
+				gp += 4;
+				cp += 4;
+			}
+			gdkpix += stride;
+			cpix += cstride;
+		}
+#undef PREMUL_ALPHA
+	}
+	cairo_surface_mark_dirty(cs);
+	return cs;
+}
+#endif //WITH_GDK_PIXBUF
diff --git a/common/meson.build b/common/meson.build
index abe0cdcf..01736ca6 100644
--- a/common/meson.build
+++ b/common/meson.build
@@ -1,12 +1,23 @@
-lib_sway_common = static_library('sway-common',
+deps = [
+	cairo,
+	wlroots
+]
+
+if gdk_pixbuf.found()
+	deps += [gdk_pixbuf]
+endif
+
+lib_sway_common = static_library(
+	'sway-common',
 	files(
+		'cairo.c',
+		'ipc-client.c',
 		'log.c',
 		'list.c',
-		'util.c',
-		'stringop.c',
 		'readline.c',
-		'ipc-client.c'
+		'stringop.c',
+		'util.c'
 	),
-	dependencies: [ wlroots ],
+	dependencies: deps,
 	include_directories: sway_inc
 )