Correct CTRL+wheel zoom on touchpad

When we get fine-grained scroll events we shouldn't zoom 10% on every
event but scale zooming so they add up to 10% for every wheel click.

Task-number: QTBUG-49024
Change-Id: I08ac728bf1421148680de8fbbc76054ba2cce884
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/plugins/texteditor/texteditor.cpp

@@ -5476,26 +5476,25 @@ void TextEditorWidget::wheelEvent(QWheelEvent *e)
             return;
         }
 
-        const int delta = e->delta();
+        const float delta = e->angleDelta().y() / 120.f;
-        if (delta < 0)
+        if (delta != 0)
-            zoomOut();
+            zoomF(delta);
-        else if (delta > 0)
-            zoomIn();
         return;
     }
     QPlainTextEdit::wheelEvent(e);
 }
 
-void TextEditorWidget::zoomIn()
+void TextEditorWidget::zoomF(float delta)
 {
     d->clearVisibleFoldedBlock();
-    emit requestFontZoom(10);
+    float step = 10.f * delta;
-}
+    // Ensure we always zoom a minimal step in-case the resolution is more than 16x
+    if (step > 0 && step < 1)
+        step = 1;
+    else if (step < 0 && step > -1)
+        step = -1;
 
-void TextEditorWidget::zoomOut()
+    emit requestFontZoom(step);
-{
-    d->clearVisibleFoldedBlock();
-    emit requestFontZoom(-10);
 }
 
 void TextEditorWidget::zoomReset()

src/plugins/texteditor/texteditor.h

@@ -378,8 +378,7 @@ public:
     void circularPaste();
     void switchUtf8bom();
 
-    void zoomIn();
+    void zoomF(float delta);
-    void zoomOut();
     void zoomReset();
 
     void cutLine();