From c7e8ee4e622ad90c6860994a0bb8eaa9c8c80566 Mon Sep 17 00:00:00 2001
From: Allan Sandfeld Jensen <allan.jensen@qt.io>
Date: Thu, 9 Apr 2020 11:26:43 +0200
Subject: Fix image scaling on WASM platform
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Apparently it has trouble with multi-threading from the main thread.

Change-Id: Ib544d69270c2780d4a42bde6fd7f491e32f29cd2
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
---
 src/gui/painting/qimagescale_neon.cpp | 86 ++++++++++++-----------------------
 1 file changed, 28 insertions(+), 58 deletions(-)

(limited to 'src/gui/painting/qimagescale_neon.cpp')

diff --git a/src/gui/painting/qimagescale_neon.cpp b/src/gui/painting/qimagescale_neon.cpp
index 416155e139..65fe3fac3c 100644
--- a/src/gui/painting/qimagescale_neon.cpp
+++ b/src/gui/painting/qimagescale_neon.cpp
@@ -41,7 +41,7 @@
 #include "qimage.h"
 #include <private/qsimd_p.h>
 
-#if QT_CONFIG(thread)
+#if QT_CONFIG(thread) && !defined(Q_OS_WASM)
 #include "qsemaphore.h"
 #include "qthreadpool.h"
 #endif
@@ -52,6 +52,30 @@ QT_BEGIN_NAMESPACE
 
 using namespace QImageScale;
 
+template<typename T>
+static inline void multithread_pixels_function(QImageScaleInfo *isi, int dh, const T &scaleSection)
+{
+#if QT_CONFIG(thread) && !defined(Q_OS_WASM)
+    int segments = (qsizetype(isi->sh) * isi->sw) / (1<<16);
+    segments = std::min(segments, dh);
+    if (segments > 1) {
+        QSemaphore semaphore;
+        int y = 0;
+        for (int i = 0; i < segments; ++i) {
+            int yn = (dh - y) / (segments - i);
+            QThreadPool::globalInstance()->start([&, y, yn]() {
+                scaleSection(y, y + yn);
+                semaphore.release(1);
+            });
+            y += yn;
+        }
+        semaphore.acquire(segments);
+        return;
+    }
+#endif
+    scaleSection(0, dh);
+}
+
 inline static uint32x4_t qt_qimageScaleAARGBA_helper(const unsigned int *pix, int xyap, int Cxy, int step)
 {
     uint32x2_t vpix32 = vmov_n_u32(*pix);
@@ -110,25 +134,7 @@ void qt_qimageScaleAARGBA_up_x_down_y_neon(QImageScaleInfo *isi, unsigned int *d
             }
         }
     };
-#if QT_CONFIG(thread)
-    int segments = (qsizetype(isi->sh) * isi->sw) / (1<<16);
-    segments = std::min(segments, dh);
-    if (segments > 1) {
-        QSemaphore semaphore;
-        int y = 0;
-        for (int i = 0; i < segments; ++i) {
-            int yn = (dh - y) / (segments - i);
-            QThreadPool::globalInstance()->start([&, y, yn]() {
-                scaleSection(y, y + yn);
-                semaphore.release(1);
-            });
-            y += yn;
-        }
-        semaphore.acquire(segments);
-        return;
-    }
-#endif
-    scaleSection(0, dh);
+    multithread_pixels_function(isi, dh, scaleSection);
 }
 
 template<bool RGB>
@@ -170,25 +176,7 @@ void qt_qimageScaleAARGBA_down_x_up_y_neon(QImageScaleInfo *isi, unsigned int *d
             }
         }
     };
-#if QT_CONFIG(thread)
-    int segments = (qsizetype(isi->sh) * isi->sw) / (1<<16);
-    segments = std::min(segments, dh);
-    if (segments > 1) {
-        QSemaphore semaphore;
-        int y = 0;
-        for (int i = 0; i < segments; ++i) {
-            int yn = (dh - y) / (segments - i);
-            QThreadPool::globalInstance()->start([&, y, yn]() {
-                scaleSection(y, y + yn);
-                semaphore.release(1);
-            });
-            y += yn;
-        }
-        semaphore.acquire(segments);
-        return;
-    }
-#endif
-    scaleSection(0, dh);
+    multithread_pixels_function(isi, dh, scaleSection);
 }
 
 template<bool RGB>
@@ -239,25 +227,7 @@ void qt_qimageScaleAARGBA_down_xy_neon(QImageScaleInfo *isi, unsigned int *dest,
             }
         }
     };
-#if QT_CONFIG(thread)
-    int segments = (qsizetype(isi->sh) * isi->sw) / (1<<16);
-    segments = std::min(segments, dh);
-    if (segments > 1) {
-        QSemaphore semaphore;
-        int y = 0;
-        for (int i = 0; i < segments; ++i) {
-            int yn = (dh - y) / (segments - i);
-            QThreadPool::globalInstance()->start([&, y, yn]() {
-                scaleSection(y, y + yn);
-                semaphore.release(1);
-            });
-            y += yn;
-        }
-        semaphore.acquire(segments);
-        return;
-    }
-#endif
-    scaleSection(0, dh);
+    multithread_pixels_function(isi, dh, scaleSection);
 }
 
 template void qt_qimageScaleAARGBA_up_x_down_y_neon<false>(QImageScaleInfo *isi, unsigned int *dest,
-- 
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