Fixes: Optimization: Important cut-offs for QTransform.

Task:     none
RevBy:    Samuel
AutoTest: Still pass
Details:  Please do not perform (potentially expensive) calculations just for fun :)
(cherry picked from commit fac3c7b73ba2c6b39332445ae00b2fe26a578913)

2 files changed, 34 insertions, 3 deletions

diff --git a/src/gui/painting/qtransform.cpp b/src/gui/painting/qtransform.cpp
index 939a668..72bfa9c 100644
--- a/src/gui/painting/qtransform.cpp
+++ b/src/gui/painting/qtransform.cpp
@@ -399,6 +399,9 @@ QTransform QTransform::inverted(bool *invertible) const
 */
 QTransform & QTransform::translate(qreal dx, qreal dy)
 {
+    if (dx == 0 && dy == 0)
+        return *this;
+
     switch(type()) {
     case TxNone:
         affine._dx = dx;
@@ -435,7 +438,10 @@ QTransform & QTransform::translate(qreal dx, qreal dy)
 QTransform QTransform::fromTranslate(qreal dx, qreal dy)
 {
     QTransform transform(1, 0, 0, 1, dx, dy);
-    transform.m_dirty = TxTranslate;
+    if (dx == 0 && dy == 0)
+        transform.m_dirty = TxNone;
+    else
+        transform.m_dirty = TxTranslate;
     return transform;
 }
 
@@ -447,6 +453,9 @@ QTransform QTransform::fromTranslate(qreal dx, qreal dy)
 */
 QTransform & QTransform::scale(qreal sx, qreal sy)
 {
+    if (sx == 1 && sy == 1)
+        return *this;
+
     switch(type()) {
     case TxNone:
     case TxTranslate:
@@ -481,7 +490,10 @@ QTransform & QTransform::scale(qreal sx, qreal sy)
 QTransform QTransform::fromScale(qreal sx, qreal sy)
 {
     QTransform transform(sx, 0, 0, sy, 0, 0);
-    transform.m_dirty = TxScale;
+    if (sx == 1 && sy == 1)
+        transform.m_dirty = TxNone;
+    else
+        transform.m_dirty = TxScale;
     return transform;
 }
 
@@ -544,6 +556,9 @@ const qreal inv_dist_to_plane = 1. / 1024.;
 */
 QTransform & QTransform::rotate(qreal a, Qt::Axis axis)
 {
+    if (a == 0)
+        return *this;
+
     qreal sina = 0;
     qreal cosa = 0;
     if (a == 90. || a == -270.)
@@ -715,7 +730,15 @@ bool QTransform::operator!=(const QTransform &o) const
 */
 QTransform & QTransform::operator*=(const QTransform &o)
 {
-    TransformationType t = qMax(type(), o.type());
+    const TransformationType otherType = o.type();
+    if (otherType == TxNone)
+        return *this;
+
+    const TransformationType thisType = type();
+    if (thisType == TxNone)
+        return operator=(o);
+
+    TransformationType t = qMax(thisType, otherType);
     switch(t) {
     case TxNone:
         break;
diff --git a/src/gui/painting/qtransform.h b/src/gui/painting/qtransform.h
index 6c725b5..9fb080b 100644
--- a/src/gui/painting/qtransform.h
+++ b/src/gui/painting/qtransform.h
@@ -257,6 +257,8 @@ inline qreal QTransform::dy() const
 
 inline QTransform &QTransform::operator*=(qreal num)
 {
+    if (num == 1.)
+        return *this;
     affine._m11 *= num;
     affine._m12 *= num;
     m_13        *= num;
@@ -271,11 +273,15 @@ inline QTransform &QTransform::operator*=(qreal num)
 }
 inline QTransform &QTransform::operator/=(qreal div)
 {
+    if (div == 0)
+        return *this;
     div = 1/div;
     return operator*=(div);
 }
 inline QTransform &QTransform::operator+=(qreal num)
 {
+    if (num == 0)
+        return *this;
     affine._m11 += num;
     affine._m12 += num;
     m_13        += num;
@@ -290,6 +296,8 @@ inline QTransform &QTransform::operator+=(qreal num)
 }
 inline QTransform &QTransform::operator-=(qreal num)
 {
+    if (num == 0)
+        return *this;
     affine._m11 -= num;
     affine._m12 -= num;
     m_13        -= num;