Resolve GLES3 functions from the shared lib

Unfortunately the few functions that are part of the OpenGL ES 3.0
standard and are used by QtGui have to have special handling after all.
Just directly calling the functions causes issues when building on a
GLES3 capable system and deploying somewhere where only GLES2 is available.

Using eglGetProcAddress and such is not an option because the ES spec does
not guarantee that standard functions are resolvable via that mechanism.

Task-number: QTBUG-43318
Change-Id: I72f985d75ca669835839016573cbb8e4a3fb41db
Reviewed-by: Jørgen Lind <jorgen.lind@theqtcompany.com>

4 files changed, 124 insertions, 51 deletions

diff --git a/src/gui/opengl/qopenglextensions_p.h b/src/gui/opengl/qopenglextensions_p.h
index 23cfe16467..f53addaf0e 100644
--- a/src/gui/opengl/qopenglextensions_p.h
+++ b/src/gui/opengl/qopenglextensions_p.h
@@ -46,11 +46,36 @@
 //
 
 #include "qopenglfunctions.h"
+#include <QtCore/qlibrary.h>
 
 QT_BEGIN_NAMESPACE
 
 class QOpenGLExtensionsPrivate;
 
+class QOpenGLES3Helper
+{
+public:
+    QOpenGLES3Helper();
+
+    GLvoid* (QOPENGLF_APIENTRYP MapBufferRange)(GLenum target, qopengl_GLintptr offset, qopengl_GLsizeiptr length, GLbitfield access);
+    GLboolean (QOPENGLF_APIENTRYP UnmapBuffer)(GLenum target);
+    void (QOPENGLF_APIENTRYP BlitFramebuffer)(GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1, GLint dstX0, GLint dstY0, GLint dstX1, GLint dstY1, GLbitfield mask, GLenum filter);
+    void (QOPENGLF_APIENTRYP RenderbufferStorageMultisample)(GLenum target, GLsizei samples, GLenum internalFormat, GLsizei width, GLsizei height);
+
+    void (QOPENGLF_APIENTRYP GenVertexArrays)(GLsizei n, GLuint *arrays);
+    void (QOPENGLF_APIENTRYP DeleteVertexArrays)(GLsizei n, const GLuint *arrays);
+    void (QOPENGLF_APIENTRYP BindVertexArray)(GLuint array);
+    GLboolean (QOPENGLF_APIENTRYP IsVertexArray)(GLuint array);
+
+    void (QOPENGLF_APIENTRYP TexImage3D)(GLenum target, GLint level, GLint internalFormat, GLsizei width, GLsizei height, GLsizei depth, GLint border, GLenum format, GLenum type, const GLvoid *pixels);
+    void (QOPENGLF_APIENTRYP TexSubImage3D)(GLenum target, GLint level, GLint xoffset, GLint yoffset, GLint zoffset, GLsizei width, GLsizei height, GLsizei depth, GLenum format, GLenum type, const GLvoid *pixels);
+    void (QOPENGLF_APIENTRYP CompressedTexImage3D)(GLenum target, GLint level, GLenum internalFormat, GLsizei width, GLsizei height, GLsizei depth, GLint border, GLsizei imageSize, const GLvoid *data);
+    void (QOPENGLF_APIENTRYP CompressedTexSubImage3D)(GLenum target, GLint level, GLint xoffset, GLint yoffset, GLint zoffset, GLsizei width, GLsizei height, GLsizei depth, GLenum format, GLsizei imageSize, const GLvoid *data);
+
+private:
+    QLibrary m_gl;
+};
+
 class Q_GUI_EXPORT QOpenGLExtensions : public QOpenGLFunctions
 {
     Q_DECLARE_PRIVATE(QOpenGLExtensions)
@@ -102,6 +127,8 @@ public:
 
     void glGetBufferSubData(GLenum target, qopengl_GLintptr offset, qopengl_GLsizeiptr size, GLvoid *data);
 
+    QOpenGLES3Helper *gles3Helper();
+
 private:
     static bool isInitialized(const QOpenGLFunctionsPrivate *d) { return d != 0; }
 };
diff --git a/src/gui/opengl/qopenglfunctions.cpp b/src/gui/opengl/qopenglfunctions.cpp
index 44b56699df..d561e65d8e 100644
--- a/src/gui/opengl/qopenglfunctions.cpp
+++ b/src/gui/opengl/qopenglfunctions.cpp
@@ -3187,65 +3187,105 @@ static void QOPENGLF_APIENTRY qopenglfResolveVertexAttribPointer(GLuint indx, GL
 
 #endif // !QT_OPENGL_ES_2
 
+// Functions part of the OpenGL ES 3.0+ standard need special handling. These,
+// just like the 2.0 functions, are not guaranteed to be resolvable via
+// eglGetProcAddress or similar. Calling them directly is, unlike the 2.0
+// functions, not feasible because one may build the binaries on a GLES3-capable
+// system and then deploy on a GLES2-only system that does not have these
+// symbols. Until ES3 gets universally available, they have to be dlsym'ed.
+
+Q_GLOBAL_STATIC(QOpenGLES3Helper, qgles3Helper)
+
+QOpenGLES3Helper::QOpenGLES3Helper()
+{
+#ifdef Q_OS_WIN
+#ifdef QT_DEBUG
+    m_gl.setFileName(QStringLiteral("libGLESv2"));
+#else
+    m_gl.setFileName(QStringLiteral("libGLESv2d"));
+#endif
+#else
+    m_gl.setFileName(QStringLiteral("GLESv2"));
+#endif
+    if (m_gl.load()) {
+        MapBufferRange = (GLvoid* (QOPENGLF_APIENTRYP)(GLenum, qopengl_GLintptr, qopengl_GLsizeiptr, GLbitfield)) m_gl.resolve("glMapBufferRange");
+        UnmapBuffer = (GLboolean (QOPENGLF_APIENTRYP)(GLenum)) m_gl.resolve("glUnmapBuffer");
+        BlitFramebuffer = (void (QOPENGLF_APIENTRYP)(GLint, GLint, GLint, GLint, GLint, GLint, GLint, GLint, GLbitfield, GLenum)) m_gl.resolve("glBlitFramebuffer");
+        RenderbufferStorageMultisample = (void (QOPENGLF_APIENTRYP)(GLenum, GLsizei, GLenum, GLsizei, GLsizei)) m_gl.resolve("glRenderbufferStorageMultisample");
+
+        GenVertexArrays = (void (QOPENGLF_APIENTRYP)(GLsizei, GLuint *)) m_gl.resolve("glGenVertexArrays");
+        DeleteVertexArrays = (void (QOPENGLF_APIENTRYP)(GLsizei, const GLuint *)) m_gl.resolve("glDeleteVertexArrays");
+        BindVertexArray = (void (QOPENGLF_APIENTRYP)(GLuint)) m_gl.resolve("glBindVertexArray");
+        IsVertexArray = (GLboolean (QOPENGLF_APIENTRYP)(GLuint)) m_gl.resolve("glIsVertexArray");
+
+        TexImage3D = (void (QOPENGLF_APIENTRYP)(GLenum, GLint, GLint, GLsizei, GLsizei, GLsizei, GLint, GLenum, GLenum, const GLvoid *)) m_gl.resolve("glTexImage3D");
+        TexSubImage3D = (void (QOPENGLF_APIENTRYP)(GLenum, GLint, GLint, GLint, GLint, GLsizei, GLsizei, GLsizei, GLenum, GLenum, const GLvoid *)) m_gl.resolve("glTexSubImage3D");
+        CompressedTexImage3D = (void (QOPENGLF_APIENTRYP)(GLenum, GLint, GLenum, GLsizei, GLsizei, GLsizei, GLint, GLsizei, const GLvoid *)) m_gl.resolve("glCompressedTexImage3D");
+        CompressedTexSubImage3D = (void (QOPENGLF_APIENTRYP)(GLenum, GLint, GLint, GLint, GLint, GLsizei, GLsizei, GLsizei, GLenum, GLsizei, const GLvoid *)) m_gl.resolve("glCompressedTexSubImage3D");
+
+        if (!MapBufferRange || !GenVertexArrays || !TexImage3D)
+            qFatal("OpenGL ES 3.0 entry points not found");
+    } else {
+        qFatal("Failed to load libGLESv2");
+    }
+}
+
+static inline bool isES3()
+{
+    QOpenGLContext *ctx = QOpenGLContext::currentContext();
+    return ctx->isOpenGLES() && ctx->format().majorVersion() >= 3;
+}
+
 static GLvoid *QOPENGLF_APIENTRY qopenglfResolveMapBuffer(GLenum target, GLenum access)
 {
-#ifdef QT_OPENGL_ES_3
     // It is possible that GL_OES_map_buffer is present, but then having to
     // differentiate between glUnmapBufferOES and glUnmapBuffer causes extra
     // headache. QOpenGLBuffer::map() will handle this automatically, while direct
     // calls are better off with migrating to the standard glMapBufferRange.
-    if (QOpenGLContext::currentContext()->format().majorVersion() >= 3) {
+    if (isES3()) {
         qWarning("QOpenGLFunctions: glMapBuffer is not available in OpenGL ES 3.0 and up. Use glMapBufferRange instead.");
         return 0;
-    } else
-#endif
-    RESOLVE_FUNC(GLvoid *, ResolveOES, MapBuffer)(target, access);
+    } else {
+        RESOLVE_FUNC(GLvoid *, ResolveOES, MapBuffer)(target, access);
+    }
 }
 
 static GLvoid *QOPENGLF_APIENTRY qopenglfResolveMapBufferRange(GLenum target, qopengl_GLintptr offset, qopengl_GLsizeiptr length, GLbitfield access)
 {
-#ifdef QT_OPENGL_ES_3
-    if (QOpenGLContext::currentContext()->format().majorVersion() >= 3)
-        return ::glMapBufferRange(target, offset, length, access);
+    if (isES3())
+        return qgles3Helper()->MapBufferRange(target, offset, length, access);
     else
-#endif
-    RESOLVE_FUNC(GLvoid *, 0, MapBufferRange)(target, offset, length, access);
+        RESOLVE_FUNC(GLvoid *, 0, MapBufferRange)(target, offset, length, access);
 }
 
 static GLboolean QOPENGLF_APIENTRY qopenglfResolveUnmapBuffer(GLenum target)
 {
-#ifdef QT_OPENGL_ES_3
-    if (QOpenGLContext::currentContext()->format().majorVersion() >= 3)
-        return ::glUnmapBuffer(target);
+    if (isES3())
+        return qgles3Helper()->UnmapBuffer(target);
     else
-#endif
-    RESOLVE_FUNC(GLboolean, ResolveOES, UnmapBuffer)(target);
+        RESOLVE_FUNC(GLboolean, ResolveOES, UnmapBuffer)(target);
 }
 
 static void QOPENGLF_APIENTRY qopenglfResolveBlitFramebuffer(GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1,
                        GLint dstX0, GLint dstY0, GLint dstX1, GLint dstY1,
                        GLbitfield mask, GLenum filter)
 {
-#ifdef QT_OPENGL_ES_3
-    if (QOpenGLContext::currentContext()->format().majorVersion() >= 3)
-        ::glBlitFramebuffer(srcX0, srcY0, srcX1, srcY1, dstX0, dstY0, dstX1, dstY1, mask, filter);
+    if (isES3())
+        qgles3Helper()->BlitFramebuffer(srcX0, srcY0, srcX1, srcY1, dstX0, dstY0, dstX1, dstY1, mask, filter);
     else
-#endif
-    RESOLVE_FUNC_VOID(ResolveEXT | ResolveANGLE | ResolveNV, BlitFramebuffer)
-        (srcX0, srcY0, srcX1, srcY1, dstX0, dstY0, dstX1, dstY1, mask, filter);
+        RESOLVE_FUNC_VOID(ResolveEXT | ResolveANGLE | ResolveNV, BlitFramebuffer)
+            (srcX0, srcY0, srcX1, srcY1, dstX0, dstY0, dstX1, dstY1, mask, filter);
 }
 
 static void QOPENGLF_APIENTRY qopenglfResolveRenderbufferStorageMultisample(GLenum target, GLsizei samples,
                                       GLenum internalFormat,
                                       GLsizei width, GLsizei height)
 {
-#ifdef QT_OPENGL_ES_3
-    if (QOpenGLContext::currentContext()->format().majorVersion() >= 3)
-        ::glRenderbufferStorageMultisample(target, samples, internalFormat, width, height);
+    if (isES3())
+        qgles3Helper()->RenderbufferStorageMultisample(target, samples, internalFormat, width, height);
     else
-#endif
-    RESOLVE_FUNC_VOID(ResolveEXT | ResolveANGLE | ResolveNV, RenderbufferStorageMultisample)
-        (target, samples, internalFormat, width, height);
+        RESOLVE_FUNC_VOID(ResolveEXT | ResolveANGLE | ResolveNV, RenderbufferStorageMultisample)
+            (target, samples, internalFormat, width, height);
 }
 
 static void QOPENGLF_APIENTRY qopenglfResolveGetBufferSubData(GLenum target, qopengl_GLintptr offset, qopengl_GLsizeiptr size, GLvoid *data)
@@ -3494,4 +3534,9 @@ QOpenGLExtensionsPrivate::QOpenGLExtensionsPrivate(QOpenGLContext *ctx)
     GetBufferSubData = qopenglfResolveGetBufferSubData;
 }
 
+QOpenGLES3Helper *QOpenGLExtensions::gles3Helper()
+{
+    return qgles3Helper();
+}
+
 QT_END_NAMESPACE
diff --git a/src/gui/opengl/qopengltexturehelper.cpp b/src/gui/opengl/qopengltexturehelper.cpp
index 29cecf0ea8..e1e3593f4f 100644
--- a/src/gui/opengl/qopengltexturehelper.cpp
+++ b/src/gui/opengl/qopengltexturehelper.cpp
@@ -34,6 +34,7 @@
 #include "qopengltexturehelper_p.h"
 
 #include <QOpenGLContext>
+#include <private/qopenglextensions_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -242,21 +243,23 @@ QOpenGLTextureHelper::QOpenGLTextureHelper(QOpenGLContext *context)
         CompressedTexImage3D = reinterpret_cast<void (QOPENGLF_APIENTRYP)(GLenum, GLint, GLenum, GLsizei, GLsizei, GLsizei, GLint, GLsizei, const GLvoid*)>(context->getProcAddress(QByteArrayLiteral("glCompressedTexImage3DOES")));
         CompressedTexSubImage3D = reinterpret_cast<void (QOPENGLF_APIENTRYP)(GLenum, GLint, GLint, GLint, GLint, GLsizei, GLsizei, GLsizei, GLenum, GLsizei, const GLvoid*)>(context->getProcAddress(QByteArrayLiteral("glCompressedTexSubImage3DOES")));
     } else {
-#ifdef QT_OPENGL_ES_3
-        // OpenGL ES 3.0+ has glTexImage3D.
-        TexImage3D = ::glTexImage3D;
-        TexSubImage3D = ::glTexSubImage3D;
-        CompressedTexImage3D = ::glCompressedTexImage3D;
-        CompressedTexSubImage3D = ::glCompressedTexSubImage3D;
-#else
-        // OpenGL 1.2
-        TexImage3D = reinterpret_cast<void (QOPENGLF_APIENTRYP)(GLenum , GLint , GLint , GLsizei , GLsizei , GLsizei , GLint , GLenum , GLenum , const GLvoid *)>(context->getProcAddress(QByteArrayLiteral("glTexImage3D")));
-        TexSubImage3D = reinterpret_cast<void (QOPENGLF_APIENTRYP)(GLenum , GLint , GLint , GLint , GLint , GLsizei , GLsizei , GLsizei , GLenum , GLenum , const GLvoid *)>(context->getProcAddress(QByteArrayLiteral("glTexSubImage3D")));
-
-        // OpenGL 1.3
-        CompressedTexImage3D = reinterpret_cast<void (QOPENGLF_APIENTRYP)(GLenum , GLint , GLenum , GLsizei , GLsizei , GLsizei , GLint , GLsizei , const GLvoid *)>(context->getProcAddress(QByteArrayLiteral("glCompressedTexImage3D")));
-        CompressedTexSubImage3D = reinterpret_cast<void (QOPENGLF_APIENTRYP)(GLenum , GLint , GLint , GLint , GLint , GLsizei , GLsizei , GLsizei , GLenum , GLsizei , const GLvoid *)>(context->getProcAddress(QByteArrayLiteral("glCompressedTexSubImage3D")));
-#endif
+        QOpenGLContext *ctx = QOpenGLContext::currentContext();
+        if (ctx->isOpenGLES() && ctx->format().majorVersion() >= 3) {
+            // OpenGL ES 3.0+ has glTexImage3D.
+            QOpenGLES3Helper *es3 = static_cast<QOpenGLExtensions *>(ctx->functions())->gles3Helper();
+            TexImage3D = es3->TexImage3D;
+            TexSubImage3D = es3->TexSubImage3D;
+            CompressedTexImage3D = es3->CompressedTexImage3D;
+            CompressedTexSubImage3D = es3->CompressedTexSubImage3D;
+        } else {
+            // OpenGL 1.2
+            TexImage3D = reinterpret_cast<void (QOPENGLF_APIENTRYP)(GLenum , GLint , GLint , GLsizei , GLsizei , GLsizei , GLint , GLenum , GLenum , const GLvoid *)>(context->getProcAddress(QByteArrayLiteral("glTexImage3D")));
+            TexSubImage3D = reinterpret_cast<void (QOPENGLF_APIENTRYP)(GLenum , GLint , GLint , GLint , GLint , GLsizei , GLsizei , GLsizei , GLenum , GLenum , const GLvoid *)>(context->getProcAddress(QByteArrayLiteral("glTexSubImage3D")));
+
+            // OpenGL 1.3
+            CompressedTexImage3D = reinterpret_cast<void (QOPENGLF_APIENTRYP)(GLenum , GLint , GLenum , GLsizei , GLsizei , GLsizei , GLint , GLsizei , const GLvoid *)>(context->getProcAddress(QByteArrayLiteral("glCompressedTexImage3D")));
+            CompressedTexSubImage3D = reinterpret_cast<void (QOPENGLF_APIENTRYP)(GLenum , GLint , GLint , GLint , GLint , GLsizei , GLsizei , GLsizei , GLenum , GLsizei , const GLvoid *)>(context->getProcAddress(QByteArrayLiteral("glCompressedTexSubImage3D")));
+        }
     }
 
 #ifndef QT_OPENGL_ES_2
diff --git a/src/gui/opengl/qopenglvertexarrayobject.cpp b/src/gui/opengl/qopenglvertexarrayobject.cpp
index 5520dfed08..d3eadf9ae1 100644
--- a/src/gui/opengl/qopenglvertexarrayobject.cpp
+++ b/src/gui/opengl/qopenglvertexarrayobject.cpp
@@ -35,12 +35,12 @@
 
 #include <QtCore/private/qobject_p.h>
 #include <QtGui/qopenglcontext.h>
-#include <QtGui/qopenglfunctions.h>
 #include <QtGui/qoffscreensurface.h>
 
 #include <QtGui/qopenglfunctions_3_0.h>
 #include <QtGui/qopenglfunctions_3_2_core.h>
 
+#include <private/qopenglextensions_p.h>
 #include <private/qopenglvertexarrayobject_p.h>
 
 QT_BEGIN_NAMESPACE
@@ -56,16 +56,14 @@ void qtInitializeVertexArrayObjectHelper(QOpenGLVertexArrayObjectHelper *helper,
     bool tryARB = true;
 
     if (context->isOpenGLES()) {
-#ifdef QT_OPENGL_ES_3
         if (context->format().majorVersion() >= 3) {
-            helper->GenVertexArrays = ::glGenVertexArrays;
-            helper->DeleteVertexArrays = ::glDeleteVertexArrays;
-            helper->BindVertexArray = ::glBindVertexArray;
-            helper->IsVertexArray = ::glIsVertexArray;
+            QOpenGLES3Helper *es3 = static_cast<QOpenGLExtensions *>(context->functions())->gles3Helper();
+            helper->GenVertexArrays = es3->GenVertexArrays;
+            helper->DeleteVertexArrays = es3->DeleteVertexArrays;
+            helper->BindVertexArray = es3->BindVertexArray;
+            helper->IsVertexArray = es3->IsVertexArray;
             tryARB = false;
-        } else
-#endif
-        if (context->hasExtension(QByteArrayLiteral("GL_OES_vertex_array_object"))) {
+        } else if (context->hasExtension(QByteArrayLiteral("GL_OES_vertex_array_object"))) {
             helper->GenVertexArrays = reinterpret_cast<QOpenGLVertexArrayObjectHelper::qt_GenVertexArrays_t>(context->getProcAddress(QByteArrayLiteral("glGenVertexArraysOES")));
             helper->DeleteVertexArrays = reinterpret_cast<QOpenGLVertexArrayObjectHelper::qt_DeleteVertexArrays_t>(context->getProcAddress(QByteArrayLiteral("glDeleteVertexArraysOES")));
             helper->BindVertexArray = reinterpret_cast<QOpenGLVertexArrayObjectHelper::qt_BindVertexArray_t>(context->getProcAddress(QByteArrayLiteral("glBindVertexArrayOES")));