From 90e226ba50c98b5e60f74f9dce998b17117f9051 Mon Sep 17 00:00:00 2001
From: Peng Huang <penghuang@chromium.org>
Date: Tue, 7 May 2019 13:16:21 +0000
Subject: [PATCH] Fix window flash for some WMs

Bug: 956061
Change-Id: I0d8d196395e70006a8fdc770f1e4a5ba6f93dd57
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1597388
Commit-Queue: Peng Huang <penghuang@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#657215}
---
 ui/gl/BUILD.gn          |  5 ++++-
 ui/gl/gl_surface_glx.cc | 41 ++++++++++++++++++++++++++++-------------
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/ui/gl/BUILD.gn b/ui/gl/BUILD.gn
index 50df0e4085..1753dd480b 100644
--- a/ui/gl/BUILD.gn
+++ b/ui/gl/BUILD.gn
@@ -274,7 +274,10 @@ jumbo_component("gl") {
       "//build/config/linux:xext",
     ]
 
-    deps += [ "//ui/gfx/x" ]
+    deps += [
+      "//ui/base/x",
+      "//ui/gfx/x",
+    ]
   }
   if (is_win) {
     sources += [
diff --git a/ui/gl/gl_surface_glx.cc b/ui/gl/gl_surface_glx.cc
index f4c13bed18..777bf767cb 100644
--- a/ui/gl/gl_surface_glx.cc
+++ b/ui/gl/gl_surface_glx.cc
@@ -21,6 +21,7 @@
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
+#include "ui/base/x/x11_util.h"
 #include "ui/events/platform/platform_event_source.h"
 #include "ui/gfx/x/x11.h"
 #include "ui/gfx/x/x11_connection.h"
@@ -431,7 +432,9 @@ bool GLSurfaceGLX::InitializeOneOff() {
   }
 
   const XVisualInfo& visual_info =
-      gl::GLVisualPickerGLX::GetInstance()->rgba_visual();
+      ui::IsCompositingManagerPresent()
+          ? gl::GLVisualPickerGLX::GetInstance()->rgba_visual()
+          : gl::GLVisualPickerGLX::GetInstance()->system_visual();
   g_visual = visual_info.visual;
   g_depth = visual_info.depth;
   g_colormap =
@@ -581,18 +584,30 @@ bool NativeViewGLSurfaceGLX::Initialize(GLSurfaceFormat format) {
   }
   size_ = gfx::Size(attributes.width, attributes.height);
 
-  XSetWindowAttributes swa;
-  memset(&swa, 0, sizeof(swa));
-  swa.background_pixmap = 0;
-  swa.bit_gravity = NorthWestGravity;
-  swa.colormap = g_colormap;
-  swa.background_pixel = 0;
-  swa.border_pixel = 0;
-  window_ = XCreateWindow(
-      gfx::GetXDisplay(), parent_window_, 0 /* x */, 0 /* y */, size_.width(),
-      size_.height(), 0 /* border_width */, g_depth, InputOutput, g_visual,
-      CWBackPixmap | CWBitGravity | CWColormap | CWBackPixel | CWBorderPixel,
-      &swa);
+  XSetWindowAttributes swa = {
+      .background_pixmap = 0,
+      .bit_gravity = NorthWestGravity,
+      .colormap = g_colormap,
+      .background_pixel = 0,  // ARGB(0,0,0,0) for compositing WM
+      .border_pixel = 0,
+  };
+  auto value_mask = CWBackPixmap | CWBitGravity | CWColormap | CWBorderPixel;
+  if (ui::IsCompositingManagerPresent() &&
+      XVisualIDFromVisual(attributes.visual) == XVisualIDFromVisual(g_visual)) {
+    // When parent and child are using the same visual, the back buffer will be
+    // shared between parent and child. If WM compositing is enabled, we set
+    // child's background pixel to ARGB(0,0,0,0), so ARGB(0,0,0,0) will be
+    // filled to the shared buffer, when the child window is mapped. It can
+    // avoid an annoying flash when the child window is mapped below.
+    // If WM compositing is disabled, we don't set the background pixel, so
+    // nothing will be draw when the child window is mapped.
+    value_mask |= CWBackPixel;
+  }
+
+  window_ =
+      XCreateWindow(gfx::GetXDisplay(), parent_window_, 0 /* x */, 0 /* y */,
+                    size_.width(), size_.height(), 0 /* border_width */,
+                    g_depth, InputOutput, g_visual, value_mask, &swa);
   if (!window_) {
     LOG(ERROR) << "XCreateWindow failed";
     return false;