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29
30 #include "qwasmopenglcontext.h"
31 #include "qwasmintegration.h"
32 #include <EGL/egl.h>
33 #include <emscripten/val.h>
34
35 QT_BEGIN_NAMESPACE
36
QWasmOpenGLContext(const QSurfaceFormat & format)37 QWasmOpenGLContext::QWasmOpenGLContext(const QSurfaceFormat &format)
38 : m_requestedFormat(format)
39 {
40 m_requestedFormat.setRenderableType(QSurfaceFormat::OpenGLES);
41
42 // if we set one, we need to set the other as well since in webgl, these are tied together
43 if (format.depthBufferSize() < 0 && format.stencilBufferSize() > 0)
44 m_requestedFormat.setDepthBufferSize(16);
45
46 if (format.stencilBufferSize() < 0 && format.depthBufferSize() > 0)
47 m_requestedFormat.setStencilBufferSize(8);
48
49 }
50
~QWasmOpenGLContext()51 QWasmOpenGLContext::~QWasmOpenGLContext()
52 {
53 if (m_context) {
54 // Destroy GL context. Work around bug in emscripten_webgl_destroy_context
55 // which removes all event handlers on the canvas by temporarily removing
56 // emscripten's JSEvents global object.
57 emscripten::val jsEvents = emscripten::val::global("window")["JSEvents"];
58 emscripten::val::global("window").set("JSEvents", emscripten::val::undefined());
59 emscripten_webgl_destroy_context(m_context);
60 emscripten::val::global("window").set("JSEvents", jsEvents);
61 m_context = 0;
62 }
63 }
64
isOpenGLVersionSupported(QSurfaceFormat format)65 bool QWasmOpenGLContext::isOpenGLVersionSupported(QSurfaceFormat format)
66 {
67 // Version check: support WebGL 1 and 2:
68 // (ES) 2.0 -> WebGL 1.0
69 // (ES) 3.0 -> WebGL 2.0
70 // [we don't expect that new WebGL versions will be created]
71 return ((format.majorVersion() == 2 && format.minorVersion() == 0) ||
72 (format.majorVersion() == 3 && format.minorVersion() == 0));
73 }
74
maybeCreateEmscriptenContext(QPlatformSurface * surface)75 bool QWasmOpenGLContext::maybeCreateEmscriptenContext(QPlatformSurface *surface)
76 {
77 // Native emscripten/WebGL contexts are tied to a single screen/canvas. The first
78 // call to this function creates a native canvas for the given screen, subsequent
79 // calls verify that the surface is on/off the same screen.
80 QPlatformScreen *screen = surface->screen();
81 if (m_context && !screen)
82 return false; // Alternative: return true to support makeCurrent on QOffScreenSurface with
83 // no screen. However, Qt likes to substitute QGuiApplication::primaryScreen()
84 // for null screens, which foils this plan.
85 if (!screen)
86 return false;
87 if (m_context)
88 return m_screen == screen;
89
90 QString canvasId = QWasmScreen::get(screen)->canvasId();
91 m_context = createEmscriptenContext(canvasId, m_requestedFormat);
92 m_screen = screen;
93 return true;
94 }
95
createEmscriptenContext(const QString & canvasId,QSurfaceFormat format)96 EMSCRIPTEN_WEBGL_CONTEXT_HANDLE QWasmOpenGLContext::createEmscriptenContext(const QString &canvasId, QSurfaceFormat format)
97 {
98 EmscriptenWebGLContextAttributes attributes;
99 emscripten_webgl_init_context_attributes(&attributes); // Populate with default attributes
100
101 attributes.powerPreference = EM_WEBGL_POWER_PREFERENCE_HIGH_PERFORMANCE;
102 attributes.failIfMajorPerformanceCaveat = false;
103 attributes.antialias = true;
104 attributes.enableExtensionsByDefault = true;
105 attributes.majorVersion = format.majorVersion() - 1;
106 attributes.minorVersion = format.minorVersion();
107
108 // WebGL doesn't allow separate attach buffers to STENCIL_ATTACHMENT and DEPTH_ATTACHMENT
109 // we need both or none
110 bool useDepthStencil = (format.depthBufferSize() > 0 || format.stencilBufferSize() > 0);
111
112 // WebGL offers enable/disable control but not size control for these
113 attributes.alpha = format.alphaBufferSize() > 0;
114 attributes.depth = useDepthStencil;
115 attributes.stencil = useDepthStencil;
116
117 QByteArray convasSelector = "#" + canvasId.toUtf8();
118 EMSCRIPTEN_WEBGL_CONTEXT_HANDLE context = emscripten_webgl_create_context(convasSelector.constData(), &attributes);
119
120 return context;
121 }
122
format() const123 QSurfaceFormat QWasmOpenGLContext::format() const
124 {
125 return m_requestedFormat;
126 }
127
defaultFramebufferObject(QPlatformSurface * surface) const128 GLuint QWasmOpenGLContext::defaultFramebufferObject(QPlatformSurface *surface) const
129 {
130 return QPlatformOpenGLContext::defaultFramebufferObject(surface);
131 }
132
makeCurrent(QPlatformSurface * surface)133 bool QWasmOpenGLContext::makeCurrent(QPlatformSurface *surface)
134 {
135 bool ok = maybeCreateEmscriptenContext(surface);
136 if (!ok)
137 return false;
138
139 return emscripten_webgl_make_context_current(m_context) == EMSCRIPTEN_RESULT_SUCCESS;
140 }
141
swapBuffers(QPlatformSurface * surface)142 void QWasmOpenGLContext::swapBuffers(QPlatformSurface *surface)
143 {
144 Q_UNUSED(surface);
145 // No swapbuffers on WebGl
146 }
147
doneCurrent()148 void QWasmOpenGLContext::doneCurrent()
149 {
150 // No doneCurrent on WebGl
151 }
152
isSharing() const153 bool QWasmOpenGLContext::isSharing() const
154 {
155 return false;
156 }
157
isValid() const158 bool QWasmOpenGLContext::isValid() const
159 {
160 if (!(isOpenGLVersionSupported(m_requestedFormat)))
161 return false;
162
163 // Note: we get isValid() calls before we see the surface and can
164 // create a native context, so no context is also a valid state.
165 return !m_context || !emscripten_is_webgl_context_lost(m_context);
166 }
167
getProcAddress(const char * procName)168 QFunctionPointer QWasmOpenGLContext::getProcAddress(const char *procName)
169 {
170 return reinterpret_cast<QFunctionPointer>(eglGetProcAddress(procName));
171 }
172
173 QT_END_NAMESPACE
174