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Improve readability of code that destroys frame callback resources

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If a frame callback resource is destroyed, it will unregister itself
from corresponding lists in current, pending, and cached state.

However, this means that we need to be super duper careful when the
compositor wants to destroy all frame callbacks. We need to make a copy
of a frameCallbacks list; otherwise a call to removeOne() will
invalidate iterators and the compositor may crash.

Currently, that copy is made implicitly. Some people may see that code
and add qAsConst() without realizing the consequences it will lead to.

This change improves the readability of that code by making explicit
copies of frameCallbacks in code that shuts down SurfaceInterface.
This commit is contained in:
Vlad Zahorodnii 2020-10-02 08:56:06 +03:00
parent 096deea9ec
commit 430aa08714
1 changed files with 10 additions and 3 deletions
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13
src/wayland/surface_interface.cpp
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@ -54,15 +54,22 @@ SurfaceInterfacePrivate::SurfaceInterfacePrivate(SurfaceInterface *q)
SurfaceInterfacePrivate::~SurfaceInterfacePrivate()
{
for (KWaylandFrameCallback *frameCallback : current.frameCallbacks) {
// Need a copy to avoid hitting invalidated iterators in the for loop.
const QList<KWaylandFrameCallback *> currentFrameCallbacks = current.frameCallbacks;
for (KWaylandFrameCallback *frameCallback : currentFrameCallbacks) {
frameCallback->destroy();
}
for (KWaylandFrameCallback *frameCallback : pending.frameCallbacks) {
const QList<KWaylandFrameCallback *> pendingFrameCallbacks = pending.frameCallbacks;
for (KWaylandFrameCallback *frameCallback : pendingFrameCallbacks) {
frameCallback->destroy();
}
for (KWaylandFrameCallback *frameCallback : cached.frameCallbacks) {
const QList<KWaylandFrameCallback *> cachedFrameCallbacks = cached.frameCallbacks;
for (KWaylandFrameCallback *frameCallback : cachedFrameCallbacks) {
frameCallback->destroy();
}
if (current.buffer) {
current.buffer->unref();
}