From aa849658c5643a1018b96316210574d9fc460c8b Mon Sep 17 00:00:00 2001
From: Ryan Gonzalez <rymg19@gmail.com>
Date: Mon, 23 Aug 2021 12:53:19 -0500
Subject: [PATCH] xwayland: Allow controlling global output scale via
 properties

This adds a new property, _XWAYLAND_GLOBAL_OUTPUT_SCALE, to control the
global output scale from the compositor.
---
 hw/xwayland/xwayland-screen.c | 55 +++++++++++++++++++++++++++++++----
 hw/xwayland/xwayland-screen.h |  1 +
 2 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/hw/xwayland/xwayland-screen.c b/hw/xwayland/xwayland-screen.c
index c1fe34de0..aeb1c11f2 100644
--- a/hw/xwayland/xwayland-screen.c
+++ b/hw/xwayland/xwayland-screen.c
@@ -133,6 +133,37 @@ xwl_screen_get_first_output(struct xwl_screen *xwl_screen)
     return xorg_list_first_entry(&xwl_screen->output_list, struct xwl_output, link);
 }
 
+static void
+xwl_screen_set_global_scale_from_property(struct xwl_screen *screen,
+                                          PropertyPtr prop)
+{
+    CARD32 *propdata;
+
+    if (prop->type != XA_CARDINAL || prop->format != 32 || prop->size != 1) {
+        // TODO: handle warnings more cleanly.
+        LogMessageVerb(X_WARNING, 0, "Bad value for property %s.\n",
+                        NameForAtom(prop->propertyName));
+        return;
+    }
+
+    propdata = prop->data;
+    xwl_screen_set_global_scale(screen, propdata[0]);
+}
+
+static void
+xwl_screen_update_property(struct xwl_screen *screen,
+                           PropertyStateRec *propstate)
+{
+    switch (propstate->state) {
+    case PropertyNewValue:
+        xwl_screen_set_global_scale_from_property(screen, propstate->prop);
+        break;
+    case PropertyDelete:
+        xwl_screen_set_global_scale(screen, 1);
+        break;
+    }
+}
+
 static void
 xwl_property_callback(CallbackListPtr *pcbl, void *closure,
                       void *calldata)
@@ -140,19 +171,24 @@ xwl_property_callback(CallbackListPtr *pcbl, void *closure,
     ScreenPtr screen = closure;
     PropertyStateRec *rec = calldata;
     struct xwl_screen *xwl_screen;
-    struct xwl_window *xwl_window;
 
     if (rec->win->drawable.pScreen != screen)
         return;
 
-    xwl_window = xwl_window_get(rec->win);
-    if (!xwl_window)
-        return;
-
     xwl_screen = xwl_screen_get(screen);
 
-    if (rec->prop->propertyName == xwl_screen->allow_commits_prop)
+    if (rec->prop->propertyName == xwl_screen->allow_commits_prop) {
+        struct xwl_window *xwl_window;
+
+        xwl_window = xwl_window_get(rec->win);
+        if (!xwl_window)
+            return;
+
         xwl_window_update_property(xwl_window, rec);
+    }
+    else if (rec->prop->propertyName == xwl_screen->global_output_scale_prop) {
+        xwl_screen_update_property(xwl_screen, rec);
+    }
 }
 
 Bool
@@ -566,6 +602,7 @@ Bool
 xwl_screen_init(ScreenPtr pScreen, int argc, char **argv)
 {
     static const char allow_commits[] = "_XWAYLAND_ALLOW_COMMITS";
+    static const char global_output_scale[] = "_XWAYLAND_GLOBAL_OUTPUT_SCALE";
     struct xwl_screen *xwl_screen;
     Pixel red_mask, blue_mask, green_mask;
     int ret, bpc, green_bpc, i;
@@ -768,6 +805,12 @@ xwl_screen_init(ScreenPtr pScreen, int argc, char **argv)
     if (xwl_screen->allow_commits_prop == BAD_RESOURCE)
         return FALSE;
 
+    xwl_screen->global_output_scale_prop = MakeAtom(global_output_scale,
+                                                    strlen(global_output_scale),
+                                                    TRUE);
+    if (xwl_screen->global_output_scale_prop == BAD_RESOURCE)
+        return FALSE;
+
     AddCallback(&PropertyStateCallback, xwl_property_callback, pScreen);
 
     xwl_screen_roundtrip(xwl_screen);
diff --git a/hw/xwayland/xwayland-screen.h b/hw/xwayland/xwayland-screen.h
index 812387d99..7446829d0 100644
--- a/hw/xwayland/xwayland-screen.h
+++ b/hw/xwayland/xwayland-screen.h
@@ -109,6 +109,7 @@ struct xwl_screen {
     struct glamor_context *glamor_ctx;
 
     Atom allow_commits_prop;
+    Atom global_output_scale_prop;
 
     /* The preferred GLVND vendor. If NULL, "mesa" is assumed. */
     const char *glvnd_vendor;