From 1534a8d71cd176c68bc7b3e8f3562d85ef6f7dfa Mon Sep 17 00:00:00 2001
From: Hannes Janetzek <hannes.janetzek@gmail.com>
Date: Wed, 28 Dec 2016 17:16:13 +0100
Subject: [PATCH] fix texture data race (#1202)

* Lock on texture mutex when updating atlas reference counts

* squash synchronize FontContext m_atlasRefs

- don't clear textures directly in releaseAtlas. This could clear the
  atlas while it's used in layoutText, before the atlas ref count got
  updated.
---
 core/src/text/fontContext.cpp | 35 ++++++++++++++++++++---------------
 core/src/text/fontContext.h   |  2 --
 2 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/core/src/text/fontContext.cpp b/core/src/text/fontContext.cpp
index b689e0ed62..d8608cba42 100644
--- a/core/src/text/fontContext.cpp
+++ b/core/src/text/fontContext.cpp
@@ -98,13 +98,7 @@ void FontContext::releaseAtlas(std::bitset<max_textures> _refs) {
     if (!_refs.any()) { return; }
     std::lock_guard<std::mutex> lock(m_textureMutex);
     for (size_t i = 0; i < m_textures.size(); i++) {
-        if (!_refs[i]) { continue; }
-
-        if (--m_atlasRefCount[i] == 0) {
-            LOGD("CLEAR ATLAS %d", i);
-            m_atlas.clear(i);
-            m_textures[i].texData.assign(GlyphTexture::size * GlyphTexture::size, 0);
-        }
+        if (_refs[i]) { m_atlasRefCount[i] -= 1; }
     }
 }
 
@@ -216,18 +210,29 @@ bool FontContext::layoutText(TextStyle::Parameters& _params, const std::string&
     glm::vec2 offset((metrics.aabb.x + width * 0.5) * TextVertex::position_scale,
                      (metrics.aabb.y + height * 0.5) * TextVertex::position_scale);
 
+    {
+        std::lock_guard<std::mutex> lock(m_textureMutex);
+        for (; it != _quads.end(); ++it) {
 
-    for (; it != _quads.end(); ++it) {
+            if (!_refs[it->atlas]) {
+                _refs[it->atlas] = true;
+                m_atlasRefCount[it->atlas]++;
+            }
 
-        if (!_refs[it->atlas]) {
-            _refs[it->atlas] = true;
-            m_atlasRefCount[it->atlas]++;
+            it->quad[0].pos -= offset;
+            it->quad[1].pos -= offset;
+            it->quad[2].pos -= offset;
+            it->quad[3].pos -= offset;
         }
 
-        it->quad[0].pos -= offset;
-        it->quad[1].pos -= offset;
-        it->quad[2].pos -= offset;
-        it->quad[3].pos -= offset;
+        // Clear unused textures
+        for (size_t i = 0; i < m_textures.size(); i++) {
+            if (m_atlasRefCount[i] == 0) {
+                m_atlas.clear(i);
+                m_textures[i].texData.assign(GlyphTexture::size *
+                                             GlyphTexture::size, 0);
+            }
+        }
     }
 
     return true;
diff --git a/core/src/text/fontContext.h b/core/src/text/fontContext.h
index c14782a87c..17681471a2 100644
--- a/core/src/text/fontContext.h
+++ b/core/src/text/fontContext.h
@@ -88,8 +88,6 @@ class FontContext : public alfons::TextureCallback {
 
     void releaseAtlas(std::bitset<max_textures> _refs);
 
-    alfons::GlyphAtlas& atlas() { return m_atlas; }
-
     /* Update all textures batches, uploads the data to the GPU */
     void updateTextures(RenderState& rs);