gtk: Fix mouse offset in scaled gtk-gl display for VFIO/iGVT-g DMA Buf mode

The issue was reported as in https://bugs.launchpad.net/qemu/+bug/1793859

When an OpenGL accelerated GTK window is used for iGVT-g DMA Buf device, window scaling would cause guest cursor to move in undesirable velocity.

To fix this usability issue, the gtk mouse motion events was modified to scale the position of event to match the coordinates of the scaled GL surface.

---
 ui/gtk-egl.c | 10 +++++++---
 ui/gtk.c     | 19 +++++++++++++------

 2 files changed, 20 insertions(+), 9 deletions(-)

index a77c25b..824beed 100644
@@ -231,9 +231,13 @@ void gd_egl_cursor_position(DisplayChangeListener *dcl,

                             uint32_t pos_x, uint32_t pos_y) {
     VirtualConsole *vc = container_of(dcl, VirtualConsole, gfx.dcl); -
-    vc->gfx.cursor_x = pos_x;
-    vc->gfx.cursor_y = pos_y;
+    uint32_t sw = surface_width(vc->gfx.ds);
+    uint32_t sh = surface_height(vc->gfx.ds);
+    GdkWindow *window = gtk_widget_get_window(vc->gfx.drawing_area); +    uint32_t ww = gdk_window_get_width(window);
+    uint32_t wh = gdk_window_get_height(window);
+    vc->gfx.cursor_x = pos_x * ww / sw;
+    vc->gfx.cursor_y = pos_y * wh / sh;
 }

 void gd_egl_release_dmabuf(DisplayChangeListener *dcl,

index 579990b..41c82e5 100644
@@ -875,20 +875,27 @@ static gboolean gd_motion_event(GtkWidget *widget, GdkEventMotion *motion,

     x = (motion->x - mx) / vc->gfx.scale_x;
     y = (motion->y - my) / vc->gfx.scale_y;

+    bool scaled = display_opengl && !gtk_use_gl_area && s->free_scale; if (qemu_input_is_absolute()) {
+        int max_w = scaled ? ww : surface_width(vc->gfx.ds);
+        int max_h = scaled ? wh : surface_height(vc->gfx.ds);
         if (x < 0 || y < 0 ||
-            x >= surface_width(vc->gfx.ds) ||
-            y >= surface_height(vc->gfx.ds)) {
+            x >= max_w ||
+            y >= max_h) {
             return TRUE;
         }
         qemu_input_queue_abs(vc->gfx.dcl.con, INPUT_AXIS_X, x,
-                             0, surface_width(vc->gfx.ds));
+                             0, max_w); qemu_input_queue_abs(vc->gfx.dcl.con, INPUT_AXIS_Y, y,
-                             0, surface_height(vc->gfx.ds));
+                             0, max_h);
         qemu_input_event_sync();
     } else if (s->last_set && s->ptr_owner == vc) {
-        qemu_input_queue_rel(vc->gfx.dcl.con, INPUT_AXIS_X, x - s->last_x); -        qemu_input_queue_rel(vc->gfx.dcl.con, INPUT_AXIS_Y, y - s->last_y); +        int diff_x = scaled
+            ? (x - s->last_x) * surface_width(vc->gfx.ds) / ww : (x - s->last_x); +        int diff_y = scaled
+            ? (y - s->last_y) * surface_height(vc->gfx.ds) / wh : (y - s->last_y); +        qemu_input_queue_rel(vc->gfx.dcl.con, INPUT_AXIS_X, diff_x); +        qemu_input_queue_rel(vc->gfx.dcl.con, INPUT_AXIS_Y, diff_y); qemu_input_event_sync();
     }
     s->last_x = x;
--
2.7.4

Hmm, we already have logic in place to deal with that. I suspect the root cause is simply that the scale_{x,y} variables are not set properly in egl mode. Can you try the patch below?

thanks,
Gerd

========================== [ cut here ] ===========================

From: Gerd Hoffmann <[email protected]>
Date: Tue, 6 Nov 2018 13:18:39 +0100
Subject: [PATCH] try fix gtk egl cursor

---
 ui/gtk-egl.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

index a77c25b490..5420c2362b 100644
@@ -68,8 +68,15 @@ void gd_egl_draw(VirtualConsole *vc)
         return;
     }
 
+    window = gtk_widget_get_window(vc->gfx.drawing_area);
+    ww = gdk_window_get_width(window);
+    wh = gdk_window_get_height(window);
+
     if (vc->gfx.scanout_mode) {
         gd_egl_scanout_flush(&vc->gfx.dcl, 0, 0, vc->gfx.w, vc->gfx.h);
+
+        vc->gfx.scale_x = (double)ww / vc->gfx.w;
+        vc->gfx.scale_y = (double)wh / vc->gfx.h;
     } else {
         if (!vc->gfx.ds) {
             return;

@@ -77,13 +84,13 @@ void gd_egl_draw(VirtualConsole *vc)
         eglMakeCurrent(qemu_egl_display, vc->gfx.esurface,
                        vc->gfx.esurface, vc->gfx.ectx);
 
-        window = gtk_widget_get_window(vc->gfx.drawing_area);
-        ww = gdk_window_get_width(window);
-        wh = gdk_window_get_height(window);
         surface_gl_setup_viewport(vc->gfx.gls, vc->gfx.ds, ww, wh);
         surface_gl_render_texture(vc->gfx.gls, vc->gfx.ds);
 
         eglSwapBuffers(qemu_egl_display, vc->gfx.esurface);
+
+        vc->gfx.scale_x = (double)ww / surface_width(vc->gfx.ds);
+        vc->gfx.scale_y = (double)wh / surface_height(vc->gfx.ds);
     }
 }
 

@@ -232,8 +239,8 @@ void gd_egl_cursor_position(DisplayChangeListener *dcl,
 {
     VirtualConsole *vc = container_of(dcl, VirtualConsole, gfx.dcl);
 
-    vc->gfx.cursor_x = pos_x;
-    vc->gfx.cursor_y = pos_y;
+    vc->gfx.cursor_x = pos_x * vc->gfx.scale_x;
+    vc->gfx.cursor_y = pos_y * vc->gfx.scale_y;
 }
 
 void gd_egl_release_dmabuf(DisplayChangeListener *dcl,

2.9.3