[gtk/wayland-cursor-scale-for-4-6: 2/2] wayland: Make cursors have the right size

[Matthias Clasen <matthiasc src gnome org>]

commit c47759bd3dd23a4c9ab9049f20bb56efb622693a
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu May 26 22:23:31 2022 -0400

    wayland: Make cursors have the right size
    
    The Wayland protocol requires that width and height
    of cursor surfaces is an integer multiple of the
    surface scale. Make it so.
    
    Fixes: #4746

 gdk/wayland/cursor/wayland-cursor.c | 46 +++++++++++++++++++++++++++----------
 1 file changed, 34 insertions(+), 12 deletions(-)
---
diff --git a/gdk/wayland/cursor/wayland-cursor.c b/gdk/wayland/cursor/wayland-cursor.c
index 572b056b30..071824d914 100644
--- a/gdk/wayland/cursor/wayland-cursor.c
+++ b/gdk/wayland/cursor/wayland-cursor.c
@@ -203,12 +203,16 @@ static struct wl_cursor *
 wl_cursor_create_from_xcursor_images(XcursorImages *images,
                                     struct wl_cursor_theme *theme,
                                      const char *name,
-                                     unsigned int load_size)
+                                     unsigned int size,
+                                     unsigned int scale)
 {
        struct cursor *cursor;
        struct cursor_image *image;
-       int i, size;
+       int i, nbytes;
+        unsigned int load_size;
+        int width, height;
 
+        load_size = size * scale;
        cursor = malloc(sizeof *cursor);
        if (!cursor)
                return NULL;
@@ -232,22 +236,37 @@ wl_cursor_create_from_xcursor_images(XcursorImages *images,
                image->theme = theme;
                image->buffer = NULL;
 
-               image->image.width = images->images[i]->width;
-               image->image.height = images->images[i]->height;
+                /* ensure that width and height are multiples of scale */
+                width = images->images[i]->width;
+                if ((width % scale) != 0)
+                  width = (width / scale + 1) * scale;
+
+                height = images->images[i]->height;
+                if ((height % scale) != 0)
+                  height = (height / scale + 1) * scale;
+
+               image->image.width = width;
+               image->image.height = height;
                image->image.hotspot_x = images->images[i]->xhot;
                image->image.hotspot_y = images->images[i]->yhot;
                image->image.delay = images->images[i]->delay;
 
-               size = image->image.width * image->image.height * 4;
-               image->offset = shm_pool_allocate(theme->pool, size);
+               nbytes = image->image.width * image->image.height * 4;
+               image->offset = shm_pool_allocate(theme->pool, nbytes);
                if (image->offset < 0) {
                        free(image);
                        break;
                }
 
                /* copy pixels to shm pool */
-               memcpy(theme->pool->data + image->offset,
-                      images->images[i]->pixels, size);
+                /* pad at the right and bottom with transparent pixels */
+                memset (theme->pool->data + image->offset, 0, nbytes);
+                for (int y = 0; y < height; y++)
+                  {
+                    memcpy(theme->pool->data + image->offset + y * width * 4,
+                           images->images[i]->pixels + y * images->images[i]->width * 4,
+                           images->images[i]->width * 4);
+                  }
                cursor->total_delay += image->image.delay;
                cursor->cursor.images[i] = (struct wl_cursor_image *) image;
        }
@@ -264,20 +283,23 @@ wl_cursor_create_from_xcursor_images(XcursorImages *images,
 }
 
 static void
-load_cursor(struct wl_cursor_theme *theme, const char *name, unsigned int size)
+load_cursor(struct wl_cursor_theme *theme,
+            const char             *name,
+            unsigned int            size,
+            unsigned int            scale)
 {
         XcursorImages *images;
        struct wl_cursor *cursor;
         char *path;
 
         path = g_strconcat (theme->path, "/", name, NULL);
-        images = xcursor_load_images (path, size);
+        images = xcursor_load_images (path, size * scale);
         g_free (path); 
 
         if (!images)
           return;
 
-        cursor = wl_cursor_create_from_xcursor_images(images, theme, name, size);
+        cursor = wl_cursor_create_from_xcursor_images(images, theme, name, size, scale);
 
        if (cursor) {
                theme->cursor_count++;
@@ -373,7 +395,7 @@ wl_cursor_theme_get_cursor(struct wl_cursor_theme *theme,
                        return theme->cursors[i];
         }
 
-        load_cursor (theme, name, size);
+        load_cursor (theme, name, theme->size, scale);
 
         if (i < theme->cursor_count) {
                 if (size == theme->cursors[i]->size &&