QMovie: fix regression in frame delays

The recent addition of support for multi-frame (non-animation) formats
had an unwanted side effect of sometimes calling
QImageReader::nextImageDelay() when the reader is at a different
frame than intended. Fix by effectively reverting to the previous call
pattern.

Fixes: QTBUG-124227
Change-Id: I735f8d67afb17bd4c77f9b4507a71796b7d66958
Reviewed-by: Paul Olav Tvete <[email protected]>
(cherry picked from commit 5f0ed0ac0ddffd3779fae0db956df8d48d629f92)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>
(cherry picked from commit 3516762d73b0325a21b344367da51e29a89a1dbd)

2 files changed, 15 insertions, 3 deletions

diff --git a/src/gui/image/qmovie.cpp b/src/gui/image/qmovie.cpp
index 56797393544..d8fe1dc8f96 100644
--- a/src/gui/image/qmovie.cpp
+++ b/src/gui/image/qmovie.cpp
@@ -320,7 +320,7 @@ QFrameInfo QMoviePrivate::infoForFrame(int frameNumber)
     // For an animated image format, QImageIOHandler::nextImageDelay() should
     // provide the time to wait until showing the next frame; but multi-frame
     // formats are not expected to provide this value, so use 1000 ms by default.
-    const int nextFrameDelay = supportsAnimation ? reader->nextImageDelay() : 1000;
+    const auto nextFrameDelay = [&]() { return supportsAnimation ? reader->nextImageDelay() : 1000; };
 
     if (cacheMode == QMovie::CacheNone) {
         if (frameNumber != currentFrameNumber+1) {
@@ -364,7 +364,7 @@ QFrameInfo QMoviePrivate::infoForFrame(int frameNumber)
             }
             if (frameNumber > greatestFrameNumber)
                 greatestFrameNumber = frameNumber;
-            return QFrameInfo(QPixmap::fromImage(std::move(anImage)), nextFrameDelay);
+            return QFrameInfo(QPixmap::fromImage(std::move(anImage)), nextFrameDelay());
         } else if (frameNumber != 0) {
             // We've read all frames now. Return an end marker
             haveReadAll = true;
@@ -392,7 +392,7 @@ QFrameInfo QMoviePrivate::infoForFrame(int frameNumber)
                     return QFrameInfo(); // Invalid
                 }
                 greatestFrameNumber = i;
-                QFrameInfo info(QPixmap::fromImage(std::move(anImage)), nextFrameDelay);
+                QFrameInfo info(QPixmap::fromImage(std::move(anImage)), nextFrameDelay());
                 // Cache it!
                 frameMap.insert(i, info);
                 if (i == frameNumber) {
diff --git a/tests/auto/gui/image/qmovie/tst_qmovie.cpp b/tests/auto/gui/image/qmovie/tst_qmovie.cpp
index 13014e04daa..ba921a66dc0 100644
--- a/tests/auto/gui/image/qmovie/tst_qmovie.cpp
+++ b/tests/auto/gui/image/qmovie/tst_qmovie.cpp
@@ -36,6 +36,7 @@ private slots:
     void playMovie();
     void jumpToFrame_data();
     void jumpToFrame();
+    void frameDelay();
     void changeMovieFile();
 #ifndef QT_NO_WIDGETS
     void infiniteLoop();
@@ -181,6 +182,17 @@ void tst_QMovie::jumpToFrame()
     QCOMPARE(movie.currentFrameNumber(), 0);
 }
 
+void tst_QMovie::frameDelay()
+{
+    QMovie movie(QFINDTESTDATA("animations/comicsecard.gif"));
+    QList<int> frameDelays{ 200, 800, 800, 2000, 2600 };
+    for (int i = 0; i < movie.frameCount(); i++) {
+        movie.jumpToFrame(i);
+        // Processing may have taken a little time, so round to nearest 100ms
+        QCOMPARE(100 * qRound(movie.nextFrameDelay() / 100.0f), frameDelays[i]);
+    }
+}
+
 void tst_QMovie::changeMovieFile()
 {
     QMovie movie(QFINDTESTDATA("animations/comicsecard.gif"));