Add support for loading SVG icons using librsvg.

This adds a configure option --disable-librsvg, but defaults to
using the library if it is present during configure.

When enabled, Openbox will attempt to load svg image files using
the library, similar to how Imlib2 is used for other image
formats.

Since librsvg uses the libXml2 library, their errors end up in
the same global namespace as Openbox config file parsing. To
avoid this, we reset the libXml current error whenever we start
loading a file, and save the last error that occurred when we
are finished, by storing the error in the ObtXmlInst.

3 files changed, 186 insertions, 20 deletions

diff --git a/obrender/image.c b/obrender/image.c
index 196d9d1e..0164a8c8 100644
--- a/obrender/image.c
+++ b/obrender/image.c
@@ -24,6 +24,9 @@
 #ifdef USE_IMLIB2
 #include <Imlib2.h>
 #endif
+#ifdef USE_LIBRSVG
+#include <librsvg/rsvg.h>
+#endif
 
 #include <glib.h>
 
@@ -463,17 +466,164 @@ RrImage* RrImageNewFromData(RrImageCache *cache, RrPixel32 *data,
     return self;
 }
 
+#if defined(USE_IMLIB2)
+typedef struct _ImlibLoader ImlibLoader;
+
+struct _ImlibLoader
+{
+    Imlib_Image img;
+};
+
+void DestroyImlibLoader(ImlibLoader *loader)
+{
+    if (!loader)
+        return;
+
+    imlib_free_image();
+    g_slice_free(ImlibLoader, loader);
+}
+
+ImlibLoader* LoadWithImlib(gchar *path,
+                           RrPixel32 **pixel_data,
+                           gint *width,
+                           gint *height)
+{
+    ImlibLoader *loader = g_slice_new0(ImlibLoader);
+    if (!(loader->img = imlib_load_image(path))) {
+        DestroyImlibLoader(loader);
+        return NULL;
+    }
+
+    /* Get data and dimensions of the image.
+
+       WARNING: This stuff is NOT threadsafe !!
+    */
+    imlib_context_set_image(loader->img);
+    *pixel_data = imlib_image_get_data_for_reading_only();
+    *width = imlib_image_get_width();
+    *height = imlib_image_get_height();
+
+    return loader;
+}
+#endif  /* USE_IMLIB2 */
+
+#if defined(USE_LIBRSVG)
+typedef struct _RsvgLoader RsvgLoader;
+
+struct _RsvgLoader
+{
+    RsvgHandle *handle;
+    cairo_surface_t *surface;
+    RrPixel32 *pixel_data;
+};
+
+void DestroyRsvgLoader(RsvgLoader *loader)
+{
+    if (!loader)
+        return;
+
+    if (loader->pixel_data)
+        g_free(loader->pixel_data);
+    if (loader->surface)
+        cairo_surface_destroy(loader->surface);
+    if (loader->handle)
+        g_object_unref(loader->handle);
+    g_slice_free(RsvgLoader, loader);
+}
+
+RsvgLoader* LoadWithRsvg(gchar *path,
+                         RrPixel32 **pixel_data,
+                         gint *width,
+                         gint *height)
+{
+    RsvgLoader *loader = g_slice_new0(RsvgLoader);
+
+    if (!(loader->handle = rsvg_handle_new_from_file(path, NULL))) {
+        DestroyRsvgLoader(loader);
+        return NULL;
+    }
+
+    if (!rsvg_handle_close(loader->handle, NULL)) {
+        DestroyRsvgLoader(loader);
+        return NULL;
+    }
+
+    RsvgDimensionData dimension_data;
+    rsvg_handle_get_dimensions(loader->handle, &dimension_data);
+    *width = dimension_data.width;
+    *height = dimension_data.height;
+
+    loader->surface = cairo_image_surface_create(
+        CAIRO_FORMAT_ARGB32, *width, *height);
+
+    cairo_t* context = cairo_create(loader->surface);
+    gboolean success = rsvg_handle_render_cairo(loader->handle, context);
+    cairo_destroy(context);
+
+    if (!success) {
+        DestroyRsvgLoader(loader);
+        return NULL;
+    }
+
+    loader->pixel_data = g_new(guint32, *width * *height);
+
+    /*
+      Cairo has its data in ARGB with premultiplied alpha, but RrPixel32
+      non-premultipled, so convert that. Also, RrPixel32 doesn't allow
+      strides not equal to the width of the image.
+    */
+
+    /* Verify that RrPixel32 has the same ordering as cairo. */
+    g_assert(RrDefaultAlphaOffset == 24);
+    g_assert(RrDefaultRedOffset == 16);
+    g_assert(RrDefaultGreenOffset == 8);
+    g_assert(RrDefaultBlueOffset == 0);
+
+    guint32 *out_row = loader->pixel_data;
+
+    guint32 *in_row =
+        (guint32*)cairo_image_surface_get_data(loader->surface);
+    gint in_stride = cairo_image_surface_get_stride(loader->surface);
+
+    gint y;
+    for (y = 0; y < *height; ++y) {
+        gint x;
+        for (x = 0; x < *width; ++x) {
+            guchar a = in_row[x] >> 24;
+            guchar r = (in_row[x] >> 16) & 0xff;
+            guchar g = (in_row[x] >> 8) & 0xff;
+            guchar b = in_row[x] & 0xff;
+            out_row[x] =
+                ((r * 256 / (a + 1)) << RrDefaultRedOffset) +
+                ((g * 256 / (a + 1)) << RrDefaultGreenOffset) +
+                ((b * 256 / (a + 1)) << RrDefaultBlueOffset) +
+                (a << RrDefaultAlphaOffset);
+        }
+        in_row += in_stride / 4;
+        out_row += *width;
+    }
+
+    *pixel_data = loader->pixel_data;
+
+    return loader;
+}
+#endif  /* USE_LIBRSVG */
+
 RrImage* RrImageNewFromName(RrImageCache *cache, const gchar *name)
 {
-#ifndef USE_IMLIB2
-    return NULL;
-#else
     RrImage *self;
     RrImageSet *set;
-    Imlib_Image img;
     gint w, h;
     RrPixel32 *data;
     gchar *path;
+    gboolean loaded;
+
+#if defined(USE_IMLIB2)
+    ImlibLoader *imlib_loader = NULL;
+#endif
+#if defined(USE_LIBRSVG)
+    RsvgLoader *rsvg_loader = NULL;
+#endif
 
     g_return_val_if_fail(cache != NULL, NULL);
     g_return_val_if_fail(name != NULL, NULL);
@@ -488,21 +638,32 @@ RrImage* RrImageNewFromName(RrImageCache *cache, const gchar *name)
     /* XXX find the path via freedesktop icon spec (use obt) ! */
     path = g_strdup(name);
 
-    if (!(img = imlib_load_image(path)))
-        g_message("Cannot load image \"%s\" from file \"%s\"", name, path);
+    loaded = FALSE;
+#if defined(USE_LIBRSVG)
+    if (!loaded) {
+        rsvg_loader = LoadWithRsvg(path, &data, &w, &h);
+        loaded = !!rsvg_loader;
+    }
+#endif
+#if defined(USE_IMLIB2)
+    if (!loaded) {
+        imlib_loader = LoadWithImlib(path, &data, &w, &h);
+        loaded = !!imlib_loader;
+    }
+#endif
+
     g_free(path);
 
-    if (!img)
+    if (!loaded) {
+        g_message("Cannot load image \"%s\" from file \"%s\"", name, path);
+#if defined(USE_LIBRSVG)
+        DestroyRsvgLoader(rsvg_loader);
+#endif
+#if defined(USE_IMLIB2)
+        DestroyImlibLoader(imlib_loader);
+#endif
         return NULL;
-
-    /* Get data and dimensions of the image.
-
-       WARNING: This stuff is NOT threadsafe !!
-    */
-    imlib_context_set_image(img);
-    data = imlib_image_get_data_for_reading_only();
-    w = imlib_image_get_width();
-    h = imlib_image_get_height();
+    }
 
     /* get an RrImage that contains an RrImageSet with this picture in it.
        the RrImage might be new, or reused if the picture was already in the
@@ -517,9 +678,14 @@ RrImage* RrImageNewFromName(RrImageCache *cache, const gchar *name)
     self = RrImageNewFromData(cache, data, w, h);
     RrImageSetAddName(self->set, name);
 
-    imlib_free_image();
-    return self;
+#if defined(USE_LIBRSVG)
+    DestroyRsvgLoader(rsvg_loader);
+#endif
+#if defined(USE_IMLIB2)
+    DestroyImlibLoader(imlib_loader);
 #endif
+
+    return self;
 }
 
 /************************************************************************
diff --git a/obrender/obrender-3.5.pc.in b/obrender/obrender-3.5.pc.in
index 2c8a4357..8057a017 100644
--- a/obrender/obrender-3.5.pc.in
+++ b/obrender/obrender-3.5.pc.in
@@ -9,6 +9,6 @@ xlibs=@X_LIBS@
 Name: ObRender
 Description: Openbox Render Library
 Version: @RR_VERSION@
-Requires: obt-3.5 glib-2.0 xft pangoxft @PKG_CONFIG_IMLIB@
+Requires: obt-3.5 glib-2.0 xft pangoxft @PKG_CONFIG_IMLIB@ @PKG_CONFIG_LIBRSVG@
 Libs: -L${libdir} -lobrender ${xlibs}
 Cflags: -I${includedir}/openbox/@RR_VERSION@ ${xcflags}
diff --git a/obrender/render.h b/obrender/render.h
index a5d6500c..59e77660 100644
--- a/obrender/render.h
+++ b/obrender/render.h
@@ -49,7 +49,7 @@ typedef struct _RrImagePic         RrImagePic;
 typedef struct _RrImageCache       RrImageCache;
 typedef struct _RrButton           RrButton;
 
-typedef guint32 RrPixel32;  /* RGBA format */
+typedef guint32 RrPixel32;  /* ARGB format, not premultiplied alpha */
 typedef guint16 RrPixel16;
 typedef guchar  RrPixel8;