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// Copyright (C) 2018 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
#include "qwasmopenglcontext.h"
#include "qwasmoffscreensurface.h"
#include "qwasmintegration.h"
#include <EGL/egl.h>
#include <emscripten/bind.h>
#include <emscripten/val.h>
namespace {
void qtDoNothing(emscripten::val) { }
} // namespace
EMSCRIPTEN_BINDINGS(qwasmopenglcontext)
{
function("qtDoNothing", &qtDoNothing);
}
QT_BEGIN_NAMESPACE
QWasmOpenGLContext::QWasmOpenGLContext(QOpenGLContext *context)
: m_actualFormat(context->format()), m_qGlContext(context)
{
m_actualFormat.setRenderableType(QSurfaceFormat::OpenGLES);
// if we set one, we need to set the other as well since in webgl, these are tied together
if (m_actualFormat.depthBufferSize() < 0 && m_actualFormat.stencilBufferSize() > 0)
m_actualFormat.setDepthBufferSize(16);
if (m_actualFormat.stencilBufferSize() < 0 && m_actualFormat.depthBufferSize() > 0)
m_actualFormat.setStencilBufferSize(8);
}
QWasmOpenGLContext::~QWasmOpenGLContext()
{
// Destroy GL context. Work around bug in emscripten_webgl_destroy_context
// which removes all event handlers on the canvas by temporarily replacing the function
// that does the removal with a function that does nothing.
destroyWebGLContext(m_ownedWebGLContext.handle);
}
bool QWasmOpenGLContext::isOpenGLVersionSupported(QSurfaceFormat format)
{
// Version check: support WebGL 1 and 2:
// (ES) 2.0 -> WebGL 1.0
// (ES) 3.0 -> WebGL 2.0
// [we don't expect that new WebGL versions will be created]
return ((format.majorVersion() == 2 && format.minorVersion() == 0) ||
(format.majorVersion() == 3 && format.minorVersion() == 0));
}
EMSCRIPTEN_WEBGL_CONTEXT_HANDLE
QWasmOpenGLContext::obtainEmscriptenContext(QPlatformSurface *surface)
{
if (m_ownedWebGLContext.surface == surface)
return m_ownedWebGLContext.handle;
if (surface->surface()->surfaceClass() == QSurface::Offscreen) {
// Reuse the existing context for offscreen drawing, even if it happens to be a canvas
// context. This is because it is impossible to re-home an existing context to the
// new surface and works as an emulation measure.
if (m_ownedWebGLContext.handle)
return m_ownedWebGLContext.handle;
// The non-shared offscreen context is heavily limited on WASM, but we provide it
// anyway for potential pixel readbacks.
m_ownedWebGLContext =
QOpenGLContextData{ .surface = surface,
.handle = createEmscriptenContext(
static_cast<QWasmOffscreenSurface *>(surface)->id(),
m_actualFormat) };
} else {
destroyWebGLContext(m_ownedWebGLContext.handle);
// Create a full on-screen context for the window canvas.
m_ownedWebGLContext = QOpenGLContextData{
.surface = surface,
.handle = createEmscriptenContext(static_cast<QWasmWindow *>(surface)->canvasSelector(),
m_actualFormat)
};
}
EmscriptenWebGLContextAttributes actualAttributes;
EMSCRIPTEN_RESULT attributesResult = emscripten_webgl_get_context_attributes(m_ownedWebGLContext.handle, &actualAttributes);
if (attributesResult == EMSCRIPTEN_RESULT_SUCCESS) {
if (actualAttributes.majorVersion == 1) {
m_actualFormat.setMajorVersion(2);
} else if (actualAttributes.majorVersion == 2) {
m_actualFormat.setMajorVersion(3);
}
m_actualFormat.setMinorVersion(0);
}
return m_ownedWebGLContext.handle;
}
void QWasmOpenGLContext::destroyWebGLContext(EMSCRIPTEN_WEBGL_CONTEXT_HANDLE contextHandle)
{
if (!contextHandle)
return;
emscripten::val jsEvents = emscripten::val::module_property("JSEvents");
emscripten::val savedRemoveAllHandlersOnTargetFunction = jsEvents["removeAllHandlersOnTarget"];
jsEvents.set("removeAllHandlersOnTarget", emscripten::val::module_property("qtDoNothing"));
emscripten_webgl_destroy_context(contextHandle);
jsEvents.set("removeAllHandlersOnTarget", savedRemoveAllHandlersOnTargetFunction);
}
EMSCRIPTEN_WEBGL_CONTEXT_HANDLE
QWasmOpenGLContext::createEmscriptenContext(const std::string &canvasSelector,
QSurfaceFormat format)
{
EmscriptenWebGLContextAttributes attributes;
emscripten_webgl_init_context_attributes(&attributes); // Populate with default attributes
attributes.powerPreference = EM_WEBGL_POWER_PREFERENCE_HIGH_PERFORMANCE;
attributes.failIfMajorPerformanceCaveat = false;
attributes.antialias = true;
attributes.enableExtensionsByDefault = true;
attributes.majorVersion = 2; // try highest supported version ES3.0 / WebGL 2.0
attributes.minorVersion = 0; // emscripten only supports minor version 0
// WebGL doesn't allow separate attach buffers to STENCIL_ATTACHMENT and DEPTH_ATTACHMENT
// we need both or none
const bool useDepthStencil = (format.depthBufferSize() > 0 || format.stencilBufferSize() > 0);
// WebGL offers enable/disable control but not size control for these
attributes.alpha = format.alphaBufferSize() > 0;
attributes.depth = useDepthStencil;
attributes.stencil = useDepthStencil;
EMSCRIPTEN_RESULT contextResult = emscripten_webgl_create_context(canvasSelector.c_str(), &attributes);
if (contextResult <= 0) {
// fallback to opengles2/webgl1
// for devices that do not support opengles3/webgl2
attributes.majorVersion = 1;
contextResult = emscripten_webgl_create_context(canvasSelector.c_str(), &attributes);
}
return contextResult;
}
QSurfaceFormat QWasmOpenGLContext::format() const
{
return m_actualFormat;
}
GLuint QWasmOpenGLContext::defaultFramebufferObject(QPlatformSurface *surface) const
{
return QPlatformOpenGLContext::defaultFramebufferObject(surface);
}
bool QWasmOpenGLContext::makeCurrent(QPlatformSurface *surface)
{
static bool sentSharingWarning = false;
if (!sentSharingWarning && isSharing()) {
qWarning() << "The functionality for sharing OpenGL contexts is limited, see documentation";
sentSharingWarning = true;
}
if (auto *shareContext = m_qGlContext->shareContext())
return shareContext->makeCurrent(surface->surface());
const auto context = obtainEmscriptenContext(surface);
if (!context)
return false;
m_usedWebGLContextHandle = context;
return emscripten_webgl_make_context_current(context) == EMSCRIPTEN_RESULT_SUCCESS;
}
void QWasmOpenGLContext::swapBuffers(QPlatformSurface *surface)
{
Q_UNUSED(surface);
// No swapbuffers on WebGl
}
void QWasmOpenGLContext::doneCurrent()
{
// No doneCurrent on WebGl
}
bool QWasmOpenGLContext::isSharing() const
{
return m_qGlContext->shareContext();
}
bool QWasmOpenGLContext::isValid() const
{
if (!isOpenGLVersionSupported(m_actualFormat))
return false;
// Note: we get isValid() calls before we see the surface and can
// create a native context, so no context is also a valid state.
return !m_usedWebGLContextHandle || !emscripten_is_webgl_context_lost(m_usedWebGLContextHandle);
}
QFunctionPointer QWasmOpenGLContext::getProcAddress(const char *procName)
{
return reinterpret_cast<QFunctionPointer>(eglGetProcAddress(procName));
}
QT_END_NAMESPACE
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