Fix base level for generateMipmap in blink

Source/modules/webgl/WebGLTexture.cpp

Index: Source/modules/webgl/WebGLTexture.cpp
diff --git a/Source/modules/webgl/WebGLTexture.cpp b/Source/modules/webgl/WebGLTexture.cpp
index 16b651875b1ab555d8a3a9da1afc1fecb2a02618..4d4e4ac6ab4b62f9294dd0217ef097632cbe2a91 100644
--- a/Source/modules/webgl/WebGLTexture.cpp
+++ b/Source/modules/webgl/WebGLTexture.cpp
@@ -214,15 +214,14 @@ void WebGLTexture::generateMipmapLevelInfo()
     if (!canGenerateMipmaps())
         return;
     if (!m_isComplete) {
-        size_t baseLevel = std::min(m_baseLevel, m_info[0].size() - 1);
         for (size_t ii = 0; ii < m_info.size(); ++ii) {
-            const LevelInfo& info0 = m_info[ii][baseLevel];
+            const LevelInfo& info0 = m_info[ii][m_baseLevel];
             GLsizei width = info0.width;
             GLsizei height = info0.height;
             GLsizei depth = info0.depth;
             GLint levelCount = computeLevelCount(width, height, depth);
-            size_t maxLevel = m_isWebGL2OrHigher ? std::min(m_maxLevel, baseLevel + levelCount - 1) : baseLevel + levelCount - 1;
-            for (size_t level = baseLevel + 1; level <= maxLevel; ++level) {
+            size_t maxLevel = m_isWebGL2OrHigher ? std::min(m_maxLevel, m_baseLevel + levelCount - 1) : m_baseLevel + levelCount - 1;
+            for (size_t level = m_baseLevel + 1; level <= maxLevel; ++level) {
                 width = std::max(1, width >> 1);
                 height = std::max(1, height >> 1);
                 depth = std::max(1, depth >> 1);
@@ -354,10 +353,11 @@ bool WebGLTexture::canGenerateMipmaps()
     if (!m_isWebGL2OrHigher && isNPOT())
         return false;
 
-    size_t baseLevel = std::min(m_baseLevel, m_info[0].size() - 1);
-    const LevelInfo& base = m_info[0][baseLevel];
+    if (m_baseLevel >= m_info[0].size())
+        return false;
+    const LevelInfo& base = m_info[0][m_baseLevel];
     for (size_t ii = 0; ii < m_info.size(); ++ii) {
-        const LevelInfo& info = m_info[ii][baseLevel];
+        const LevelInfo& info = m_info[ii][m_baseLevel];
         if (!info.valid
             || info.width != base.width || info.height != base.height || info.depth != base.depth
             || info.internalFormat != base.internalFormat || info.type != base.type
@@ -399,17 +399,18 @@ void WebGLTexture::update()
     m_isComplete = true;
     m_isCubeComplete = true;
 
-    size_t baseLevel = std::min(m_baseLevel, m_info[0].size() - 1);
-    const LevelInfo& base = m_info[0][baseLevel];
+    if (m_baseLevel >= m_info[0].size())
+        return;

[Zhenyao Mo, 2015/09/07 21:35:17]

should m_isComplete be set to false?

[qiankun, 2015/09/08 03:35:06]

Done.

+    const LevelInfo& base = m_info[0][m_baseLevel];
     size_t levelCount = computeLevelCount(base.width, base.height, base.depth);
-    size_t maxLevel = m_isWebGL2OrHigher ? std::min(m_maxLevel, baseLevel + levelCount - 1) : baseLevel + levelCount - 1;
+    size_t maxLevel = m_isWebGL2OrHigher ? std::min(m_maxLevel, m_baseLevel + levelCount - 1) : m_baseLevel + levelCount - 1;
 
-    if (baseLevel > maxLevel) {
+    if (m_baseLevel > maxLevel) {

[Zhenyao Mo, 2015/09/07 21:35:18]

As I mentioned in the other CL, my reading of the spec is maxLevel should be
clamped to [baseLevel, max], not generate an error instead.

[qiankun, 2015/09/08 03:35:06]

Just set m_isComplete as false here other than returning false. This is
limitation of texture completeness.

[Zhenyao Mo, 2015/09/08 20:45:24]

So I read the ES spec 3.0.4 one more time, here are my understandings.

Section 3.8.10 Texture Minification, under "Mipmapping", page 158, "For
immutable-format textures, level base is clamped to the range [0, levels − 1],
level max is then clamped to the range [level base , levels − 1], and p is one
less than levels, where levels is the parameter passed to TexStorage* for the
texture object (see section 3.8.4). Otherwise p = log 2 (maxsize) + level base ,
and all arrays from level base through q = min{p, level max } must be defined,
as discussed in section 3.8.13."

Section 3.8.13 Texture Completeness says one necessary condition for a texture
to be complete is level base <= level max. It didn't mention anything about
clamping for immutable textures.

kbr, bajones: inputs?

[Zhenyao Mo, 2015/09/08 21:11:17]

In Section 3.9.2 Shader Execution, Texture Access, it simply referes to Section
3.8.12 Texture Completeness. So let's respect Section 3.8.12's definition for
all textures, including immutable textures.

         m_isComplete = false;
     }
     else {
         for (size_t ii = 0; ii < m_info.size() && m_isComplete; ++ii) {
-            const LevelInfo& info0 = m_info[ii][baseLevel];
+            const LevelInfo& info0 = m_info[ii][m_baseLevel];
             if (!info0.valid
                 || info0.width != base.width || info0.height != base.height || info0.depth != base.depth
                 || info0.internalFormat != base.internalFormat || info0.type != base.type
@@ -422,7 +423,7 @@ void WebGLTexture::update()
             GLsizei width = info0.width;
             GLsizei height = info0.height;
             GLsizei depth = info0.depth;
-            for (size_t level = baseLevel + 1; level <= maxLevel; ++level) {
+            for (size_t level = m_baseLevel + 1; level <= maxLevel; ++level) {
                 width = std::max(1, width >> 1);
                 height = std::max(1, height >> 1);
                 depth = std::max(1, depth >> 1);