With QtQuick2 it's possible that the scene graph rendering context either
lives in an own thread or uses the main GUI thread. In the latter case
it's the same thread as our compositing OpenGL context lives in. This
means our basic assumption that between two rendering passes the context
stays current does not hold.
The code already ensured that before we start a rendering pass the
context is made current, but there are many more possible cases. If we
use OpenGL in areas not triggered by the rendering loop but in response
to other events the context needs to be made current. This includes the
loading and unloading of effects (some effects use OpenGL in the static
effect check, in the ctor and dtor), background loading of texture data,
lazy loading after first usage invoked by shortcut, etc. etc.
To properly handle these cases new methods are added to EffectsHandler
to make the compositing OpenGL context current. These calls delegate down
into the scene. On non-OpenGL scenes they are noop, but on OpenGL they go
into the backend and make the context current. In addition they ensure
that Qt doesn't think that it's QOpenGLContext is current by calling
doneCurrent() on the QOpenGLContext::currentContext(). This unfortunately
causes an additional call to makeCurrent with a null context, but there
is no other way to tell Qt - it doesn't notice when a different context
is made current with low level API calls. In the multi-threaded
architecture this doesn't matter as ::currentContext() returns null.
A short evaluation showed that a transition to QOpenGLContext doesn't
seem feasible. Qt only supports either GLX or EGL while KWin supports
both and when entering the transition phase for Wayland, it would become
extremely tricky if our native platform is X11, but we want a Wayland
EGL context. A future solution might be to have a "KWin-QPA plugin" which
uses either xcb or Wayland and hides everything from Qt.
The API documentation is extended to describe when the effects-framework
ensures that an OpenGL context is current. The effects are changed to
make the context current in cases where it's not guaranteed. This has
been done by looking for creation or deletion of GLTextures and Shaders.
If there are other OpenGL usages outside the rendering loop, ctor/dtor
this needs to be changed, too.
* "" needs to be wrapped in QStringLiteral
* QString::fromUtf8 needed for const char* and QByteArray
* QByteArray::constData() needed to get to the const char*
If the build option is enabled KWIN_HAVE_OPENGL_1 is passed as a compile
flag when build against OpenGL.
This compile flag is meant to replace the KWIN_HAVE_OPENGLES. So far code
has been ifdefed for special behavior of OpenGL ES 2.0 and to remove
fixed functionality calls which are not available in OpenGL ES 2.0.
With this build flag the fixed functionality calls which are only used in
the OpenGL1 Compositor can be removed and keeping the KWIN_HAVE_OPENGLES
for the real differences between OpenGL 2.x and OpenGL ES 2.0.
E.g. a call like glColor4f should be in an
glColor4f(1.0, 1.0, 1.0, 1.0);
while a call like glPolygonMode should be in an
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
Building for OpenGL ES 2.0 of course implies that KWIN_HAVE_OPENGL_1 is
not defined.
The main usage of ShaderManager::isValid was to have OpenGL2 specific
code pathes. Now we have an actual OpenGL2Compositing type and we know
that the ShaderManager is valid if we have this compositing type and we
know that it is not valid on OpenGL1Compositing. This gives us a much
better check and allows us to use the isValid method just for where we
want to check whether the shaders compiled successfully.
In addition some effects require OpenGL2, so we do not need to check
again that the ShaderManager is valid. Such usages are removed.
The CompositingType enum turns into flags and two new values are
introduced: OpenGL1Compositing and OpenGL2Compositing.
Those new values are or-ed to OpenGLCompositing so that a simple check
for the flag OpenGLCompositing works in case of one of those two new
values. To make the generic check for OpenGL compositing easier a method
in EffectsHandler is introduced to just check for this.
The scenes now return either OpenGL1Compositing or OpenGL2Compositing
depending on which Scene implementation. None returns OpenGLCompositing.
Effects can specify their minimum requirements in their
desktop file:
* OpenGL
* OpenGL 2 (GLSL required)
* Shaders (either ARB or OpenGL 2)
The configuration module uses this information in combination
with which backend KWin is currently using. So if e.g. OpenGL
is used and an effect requires OpenGL 2 a detailed error
message can be showed that OpenGL 2 is required.
BUG: 209213
FIXED-IN: 4.9.0
REVIEW: 104847
This makes kwin in OpenGL2 mode more coherent with kwin_gles.
Despite some fullscreen effects they should now make the same
(pure) OpenGL calls.
REVIEW: 103804
Each effect is able to declare itself as currently being active,
that is transforming windows or painting or screen or doing anything
during the current rendered frame.
This change eliminates the hottest path inside KWin identified by
callgrind.
REVIEW: 102449
The uniforms textureWidth and textureHeight were only needed for
normal windows. For everything else it was just 1.0/1.0, that is
normalized.
The makeArrays method is changed to produce normalized texcoords
obsoleting the need for these uniforms. So two uniforms less, one
calculation in vertex shaders less and many many lines of code
removed.
At the same time makeArrays is also adjusted to take care of
yInverted of the texture, which is needed as we no longer can use
the enableUnnormalizedTexCoords which did the yInverted transformation.
REVIEW: 101646
