Inform compositor of visible window geometry

The numbers dont make logical sense, but they do what is expected on
GNOME and since only GNOME is stupid enough to insist on CSD, that's
all we care about.

glfw/wl_client_side_decorations.c

@@ -392,3 +392,19 @@ change_csd_title(_GLFWwindow *window) {
         damage_csd(top, decs.top.buffer.front);
     }
 }
+
+void
+set_csd_window_geometry(_GLFWwindow *window, int32_t *width, int32_t *height) {
+    bool has_csd = window->decorated && !window->wl.decorations.serverSide && window->wl.decorations.left.surface && !window->wl.fullscreened;
+    bool size_specified_by_compositor = *width > 0 && *height > 0;
+    if (!size_specified_by_compositor) { *width = window->wl.width; *height = window->wl.height; }
+    struct { int32_t x, y, width, height; } geometry = {.x = 0, .y = 0, .width = *width, .height = *height};
+    int scale = window->wl.scale >= 1 ? window->wl.scale : 1;
+    if (has_csd) {
+        int32_t visible_titlebar_height = decs.metrics.top - decs.metrics.width;
+        geometry.y = -decs.metrics.top + decs.metrics.width / scale;
+        geometry.height = *height;
+        *height -= visible_titlebar_height;
+    }
+    xdg_surface_set_window_geometry(window->wl.xdg.surface, geometry.x, geometry.y, geometry.width, geometry.height);
+}

glfw/wl_client_side_decorations.h

@@ -13,3 +13,4 @@ void free_csd_surfaces(_GLFWwindow *window);
 void resize_csd(_GLFWwindow *window);
 void change_csd_title(_GLFWwindow *window);
 bool ensure_csd_resources(_GLFWwindow *window);
+void set_csd_window_geometry(_GLFWwindow *window, int32_t *width, int32_t *height);

glfw/wl_window.c

@@ -237,8 +237,6 @@ clipboard_mime(void) {
 }
 
 static void dispatchChangesAfterConfigure(_GLFWwindow *window, int32_t width, int32_t height) {
-    if (width <= 0) width = window->wl.width;
-    if (height <= 0) height = window->wl.height;
     bool size_changed = width != window->wl.width || height != window->wl.height;
     bool scale_changed = checkScaleChange(window);
 
@@ -444,12 +442,8 @@ static void xdgToplevelHandleConfigure(void* data,
         }
     }
     window->wl.fullscreened = fullscreen;
-    if (!fullscreen) {
-        if (window->decorated && !window->wl.decorations.serverSide && window->wl.decorations.left.surface) {
-            width -= window->wl.decorations.metrics.horizontal;
-            height -= window->wl.decorations.metrics.vertical;
-        }
-    }
+    set_csd_window_geometry(window, &width, &height);
+    wl_surface_commit(window->wl.surface);
     dispatchChangesAfterConfigure(window, width, height);
     _glfwInputWindowFocus(window, activated);
     ensure_csd_resources(window);