Polish the Mandelbrot Example

Fix warnings about float constants and comparison.
Use member or constructor initialization.
Introduce some const for clarity.
Use Qt_CONFIG.

Task-number: QTBUG-81254
Change-Id: I71a6ebfba397c0f8e1dd2e61167233c8e5c137af
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

1 files changed, 12 insertions, 15 deletions

diff --git a/examples/corelib/threads/mandelbrot/renderthread.cpp b/examples/corelib/threads/mandelbrot/renderthread.cpp
index eee44c7242..22ce81c32d 100644
--- a/examples/corelib/threads/mandelbrot/renderthread.cpp
+++ b/examples/corelib/threads/mandelbrot/renderthread.cpp
@@ -57,9 +57,6 @@
 RenderThread::RenderThread(QObject *parent)
     : QThread(parent)
 {
-    restart = false;
-    abort = false;
-
     for (int i = 0; i < ColormapSize; ++i)
         colormap[i] = rgbFromWaveLength(380.0 + (i * 400.0 / ColormapSize));
 }
@@ -102,10 +99,10 @@ void RenderThread::run()
 {
     forever {
         mutex.lock();
-        QSize resultSize = this->resultSize;
-        double scaleFactor = this->scaleFactor;
-        double centerX = this->centerX;
-        double centerY = this->centerY;
+        const QSize resultSize = this->resultSize;
+        const double scaleFactor = this->scaleFactor;
+        const double centerX = this->centerX;
+        const double centerY = this->centerY;
         mutex.unlock();
 //! [3]
 
@@ -128,20 +125,20 @@ void RenderThread::run()
                 if (abort)
                     return;
 
-                uint *scanLine =
+                auto scanLine =
                         reinterpret_cast<uint *>(image.scanLine(y + halfHeight));
-                double ay = centerY + (y * scaleFactor);
+                const double ay = centerY + (y * scaleFactor);
 
                 for (int x = -halfWidth; x < halfWidth; ++x) {
-                    double ax = centerX + (x * scaleFactor);
+                    const double ax = centerX + (x * scaleFactor);
                     double a1 = ax;
                     double b1 = ay;
                     int numIterations = 0;
 
                     do {
                         ++numIterations;
-                        double a2 = (a1 * a1) - (b1 * b1) + ax;
-                        double b2 = (2 * a1 * b1) + ay;
+                        const double a2 = (a1 * a1) - (b1 * b1) + ax;
+                        const double b2 = (2 * a1 * b1) + ay;
                         if ((a2 * a2) + (b2 * b2) > Limit)
                             break;
 
@@ -187,9 +184,9 @@ void RenderThread::run()
 //! [10]
 uint RenderThread::rgbFromWaveLength(double wave)
 {
-    double r = 0.0;
-    double g = 0.0;
-    double b = 0.0;
+    double r = 0;
+    double g = 0;
+    double b = 0;
 
     if (wave >= 380.0 && wave <= 440.0) {
         r = -1.0 * (wave - 440.0) / (440.0 - 380.0);