tdf#165606 fix: master slide panel doesn't resized correctly in gtk

- follow up to 98b86bff2c
- the problem was get_rect give 0 height when preview are loading.
- this patch fixes the problem by taking image size from
MasterPageContainer

Change-Id: Ie4a3e25826e871ae5cbda58edba092e9a3eae193
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/182806
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Tested-by: Jenkins

sd/source/ui/sidebar/MasterPageContainer.cxx

@@ -103,6 +103,8 @@ public:
 
     void ReleaseDescriptor (Token aToken);
 
+    const Size& GetPreviewSizePixel(PreviewSize pPreviewSize);
+
     /** Called by the MasterPageContainerFiller to notify that all master
         pages from template documents have been added.
     */
@@ -444,6 +446,11 @@ void MasterPageContainer::InvalidatePreview (MasterPageContainer::Token aToken)
     mpImpl->InvalidatePreview(aToken);
 }
 
+const Size& MasterPageContainer::GetPreviewSizePixel()
+{
+    return mpImpl->GetPreviewSizePixel(mePreviewSize);
+}
+
 Image MasterPageContainer::GetPreviewForToken (MasterPageContainer::Token aToken)
 {
     return mpImpl->GetPreviewForToken(aToken,mePreviewSize);
@@ -809,6 +816,14 @@ SdDrawDocument* MasterPageContainer::Implementation::GetDocument()
     return mpDocument;
 }
 
+const Size& MasterPageContainer::Implementation::GetPreviewSizePixel(PreviewSize pPreviewSize)
+{
+    if (pPreviewSize == PreviewSize::SMALL)
+        return maSmallPreviewSizePixel;
+    else
+        return maLargePreviewSizePixel;
+}
+
 Image MasterPageContainer::Implementation::GetPreviewSubstitution (
     TranslateId pId,
     PreviewSize ePreviewSize)

sd/source/ui/sidebar/MasterPageContainer.hxx

@@ -85,6 +85,8 @@ public:
     };
     PreviewState GetPreviewState(Token aToken);
 
+    const Size& GetPreviewSizePixel();
+
     /** This method is typically called for entries in the container for
         which GetPreviewState() returns OS_CREATABLE.  The creation of the
         preview is then scheduled to be executed asynchronously at a later

sd/source/ui/sidebar/MasterPagesSelector.cxx

@@ -585,7 +585,8 @@ css::ui::LayoutSize MasterPagesSelector::GetHeightForWidth(const sal_Int32 nWidt
 {
     // there is no way to get margin of item programmatically, we use value provided in ui file.
     const int nMargin = 6;
-    sal_Int32 nColumnCount = nWidth / (mxPreviewIconView->get_item_width() + (5 * nMargin));
+    const Size& previewSize = mpContainer->GetPreviewSizePixel();
+    sal_Int32 nColumnCount = nWidth / (previewSize.Width() + (2 * nMargin));
     if (nColumnCount < 1)
         nColumnCount = 1;
 
@@ -594,8 +595,7 @@ css::ui::LayoutSize MasterPagesSelector::GetHeightForWidth(const sal_Int32 nWidt
     if (nRowCount < 1)
         nRowCount = 1;
 
-    sal_Int32 nPreferedHeight
-        = nRowCount * (mxPreviewIconView->get_rect(nTotalItems - 1).GetHeight() + (2 * nMargin));
+    sal_Int32 nPreferedHeight = nRowCount * (previewSize.getHeight() + (4 * nMargin));
     return css::ui::LayoutSize(nPreferedHeight, nPreferedHeight, nPreferedHeight);
 }