Dialog: Fix poisitioning and theme rendering

- updateTheme should always be called the frameSvgItem's size has been
  upated. It uses the geometry of the frameSvgItem. Also updated the
  documentation.

- When a dialog has a visualParent, setting the position of the dialog
  is slightly compilcated. In order to set the position we have to give
  the function popupPosition the size of the dialog so that it can
  determine where to place it, however the size of the dialog depends on
  the position as some of the borders are drawn depending on the
  position. We have a circular problem.

  For now we're solving this by tempoarily giving the full size with all
  the borders in the case when there is a visual parent.

src/plasmaquick/dialog.cpp

@@ -70,7 +70,19 @@ public:
     void updateInputShape();
 
     //SLOTS
+    /**
+     * Sync Borders updates the enabled borders of the frameSvgItem depending
+     * on the geometry of the window.
+     * Make sure the window is in the correct position + size before calling
+     * this function
+     */
     void syncBorders();
+
+    /**
+     * This function sets the blurBehind, background contrast and shadows. It
+     * does so wrt the frameSvgItem. So make sure the frameSvgItem is the
+     * correct size before calling this function.
+     */
     void updateTheme();
     void updateVisibility(bool visible);
 
@@ -262,7 +274,6 @@ void DialogPrivate::updateMinimumWidth()
     mainItem->disconnect(q);
 
     syncBorders();
-    updateTheme();
 
     int minimumWidth = mainItemLayout->property("minimumWidth").toInt();
     auto margin = frameSvgItem->margins();
@@ -279,6 +290,7 @@ void DialogPrivate::updateMinimumWidth()
         q->setX(q->x() + (oldWidth - q->size().width()));
     }
     repositionIfOffScreen();
+    updateTheme();
 
     QObject::connect(mainItem, SIGNAL(widthChanged()), q, SLOT(slotMainItemSizeChanged()));
     QObject::connect(mainItem, SIGNAL(heightChanged()), q, SLOT(slotMainItemSizeChanged()));
@@ -292,7 +304,6 @@ void DialogPrivate::updateMinimumHeight()
     mainItem->disconnect(q);
 
     syncBorders();
-    updateTheme();
 
     int minimumHeight = mainItemLayout->property("minimumHeight").toInt();
     auto margin = frameSvgItem->margins();
@@ -309,6 +320,7 @@ void DialogPrivate::updateMinimumHeight()
         q->setY(q->y() + (oldHeight - q->size().height()));
     }
     repositionIfOffScreen();
+    updateTheme();
 
     QObject::connect(mainItem, SIGNAL(widthChanged()), q, SLOT(slotMainItemSizeChanged()));
     QObject::connect(mainItem, SIGNAL(heightChanged()), q, SLOT(slotMainItemSizeChanged()));
@@ -322,7 +334,6 @@ void DialogPrivate::updateMaximumWidth()
     mainItem->disconnect(q);
 
     syncBorders();
-    updateTheme();
 
     int maximumWidth = mainItemLayout->property("maximumWidth").toInt();
     maximumWidth = maximumWidth ? maximumWidth : DIALOGSIZE_MAX;
@@ -335,6 +346,7 @@ void DialogPrivate::updateMaximumWidth()
     frameSvgItem->setWidth(q->width());
 
     repositionIfOffScreen();
+    updateTheme();
 
     QObject::connect(mainItem, SIGNAL(widthChanged()), q, SLOT(slotMainItemSizeChanged()));
     QObject::connect(mainItem, SIGNAL(heightChanged()), q, SLOT(slotMainItemSizeChanged()));
@@ -348,7 +360,6 @@ void DialogPrivate::updateMaximumHeight()
     mainItem->disconnect(q);
 
     syncBorders();
-    updateTheme();
 
     int maximumHeight = mainItemLayout->property("maximumHeight").toInt();
     maximumHeight = maximumHeight ? maximumHeight : DIALOGSIZE_MAX;
@@ -361,6 +372,7 @@ void DialogPrivate::updateMaximumHeight()
     frameSvgItem->setHeight(q->height());
 
     repositionIfOffScreen();
+    updateTheme();
 
     QObject::connect(mainItem, SIGNAL(widthChanged()), q, SLOT(slotMainItemSizeChanged()));
     QObject::connect(mainItem, SIGNAL(heightChanged()), q, SLOT(slotMainItemSizeChanged()));
@@ -435,10 +447,30 @@ void DialogPrivate::updateInputShape()
 
 void DialogPrivate::syncToMainItemSize()
 {
-    if (!componentComplete || !mainItem) {
+    if (!componentComplete || !mainItem || !q->isVisible()) {
         return;
     }
 
+    if (visualParent) {
+        // Get the full size with ALL the borders
+        frameSvgItem->setEnabledBorders(Plasma::FrameSvg::AllBorders);
+        auto margins = frameSvgItem->margins();
+
+        const QSize fullSize = QSize(mainItem->width(), mainItem->height()) +
+                               QSize(margins->left() + margins->right(),
+                                     margins->top() + margins->bottom());
+
+        // We get the popup position with the fullsize as we need the popup
+        // position in order to determine our actual size, as the position
+        // determines which borders will be shown.
+        const QRect geom(q->popupPosition(visualParent, fullSize), fullSize);
+
+        // We're then moving the window to where we think we would be with all
+        // the borders. This way when syncBorders is caleld, it has a geometry
+        // to work with.
+        q->adjustGeometry(geom);
+    }
+
     syncBorders();
 
     const QSize s = QSize(mainItem->width(), mainItem->height()) +
@@ -450,8 +482,8 @@ void DialogPrivate::syncToMainItemSize()
     frameSvgItem->setWidth(s.width());
     frameSvgItem->setHeight(s.height());
 
-    if (q->visualParent()) {
+    if (visualParent) {
-        const QRect geom(q->popupPosition(q->visualParent(), s), s);
+        const QRect geom(q->popupPosition(visualParent, s), s);
 
         if (geom == q->geometry()) {
             return;
@@ -576,10 +608,6 @@ void Dialog::setMainItem(QQuickItem *mainItem)
                 d->updateMinimumHeight();
                 d->updateMaximumWidth();
                 d->updateMaximumHeight();
-
-                if (visualParent()) {
-                    setPosition(popupPosition(visualParent(), size()));
-                }
             }
 
         }