Comment 4 for bug 1784900

Another patch that seems to work tries to remember the old surface:

diff --git a/hw/display/vga.c b/hw/display/vga.c
index ed476e4e80..1aae6a6d3b 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -1554,7 +1554,8 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
         height != s->last_height ||
         s->last_depth != depth ||
         s->last_byteswap != byteswap ||
- share_surface != is_buffer_shared(surface)) {
+ share_surface != is_buffer_shared(surface) ||
+ s->last_surface != surface) {
         /* display parameters changed -> need new display surface */
         s->last_scr_width = disp_width;
         s->last_scr_height = height;
@@ -1563,8 +1564,10 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
         s->last_line_offset = s->line_offset;
         s->last_depth = depth;
         s->last_byteswap = byteswap;
+ s->last_surface = surface;
         full_update = 1;
     }
+ fprintf(stderr, "%p vs %p share_surface: %d surface: %p\n", surface_data(surface), s->vram_ptr + (s->start_addr * 4), share_surface, surface);
     if (surface_data(surface) != s->vram_ptr + (s->start_addr * 4)
         && is_buffer_shared(surface)) {
         /* base address changed (page flip) -> shared display surfaces
diff --git a/hw/display/vga_int.h b/hw/display/vga_int.h
index f8fcf62a56..91afc52b0e 100644
--- a/hw/display/vga_int.h
+++ b/hw/display/vga_int.h
@@ -122,6 +122,7 @@ typedef struct VGACommonState {
     uint32_t last_width, last_height; /* in chars or pixels */
     uint32_t last_scr_width, last_scr_height; /* in pixels */
     uint32_t last_depth; /* in bits */
+ void *last_surface;
     bool last_byteswap;
     bool force_shadow;
     uint8_t cursor_start, cursor_end;