tdf#173578 vcl weld: Evaluate/Apply GtkIconView::item-padding

Instead of hard-coding the spacing for the vcl IconView
implementation to 5 pixels, use that as the default, but
override it with the GtkIconView::item-padding [1] property
if that one is set for an icon view in a .ui file.

Together with previous commit

    Change-Id: I703504b7e2ce0c4b5351a95616112950a33332dd
    Author: Michael Weghorn <m.weghorn@posteo.de>
    Date:   Wed Sep 23 11:00:24 2026 +0200

        tdf#173578 Reduce spacing between ColorIconView items

, this results in the spacing between ColorIconView items
now also being smaller than before when the vcl implementation
(SalInstanceIconView) is used.

[1] https://docs.gtk.org/gtk3/property.IconView.item-padding.html

Change-Id: If4997dd5ea40659532424c600bb74e185c69b102
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/211359
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

vcl/inc/iconview.hxx

@@ -28,6 +28,9 @@ private:
     short m_nFixedColumnCount = -1;
     short m_nColumnCount;
 
+    // number of pixels from top, from bottom, between icon and label
+    int m_nSpacing = 5;
+
 public:
     IconView(vcl::Window* pParent, WinBits nBits);
 
@@ -35,6 +38,8 @@ public:
     short GetColumnCount() const { return m_nColumnCount; }
     void SetFixedColumnCount(short nColumnCount);
 
+    void SetSpacing(int nSpacing) { m_nSpacing = nSpacing; }
+
     virtual Size GetOptimalSize() const override;
     virtual void Resize() override;
 

vcl/source/treelist/iconview.cxx

@@ -30,7 +30,6 @@
 namespace
 {
 const int separatorHeight = 10;
-const int nSpacing = 5; // 5 pixels from top, from bottom, between icon and label
 }
 
 IconView::IconView(vcl::Window* pParent, WinBits nBits)
@@ -64,7 +63,7 @@ void IconView::UpdateEntrySize(const SvTreeListEntry& rEntry)
     // provide some minimum width if text exists (will be ellipsized if it doesn't fit completely)
     const tools::Long nMinTextWidth = rEntry.GetFirstItem(SvLBoxItemType::String) ? 100 : 0;
 
-    int spacing = nSpacing * 2;
+    int spacing = m_nSpacing * 2;
     const short nMinHeight = aImageSize.getHeight() + spacing;
     const short nMinWidth = std::max(aImageSize.getWidth() + spacing, nMinTextWidth);
 
@@ -98,7 +97,7 @@ bool IconView::HasSeparatorEntry() const
 
 void IconView::CalcEntryHeight(const SvTreeListEntry& rEntry)
 {
-    int nHeight = nSpacing * 2;
+    int nHeight = m_nSpacing * 2;
     SvViewDataEntry& rViewData = GetViewDataEntry(rEntry);
     const size_t nCount = rEntry.ItemCount();
     bool bHasIcon = false;
@@ -111,7 +110,7 @@ void IconView::CalcEntryHeight(const SvTreeListEntry& rEntry)
     }
 
     if (bHasIcon && nCount > 1)
-        nHeight += nSpacing; // between icon and label
+        nHeight += m_nSpacing; // between icon and label
 
     if (nHeight > m_nEntryHeight)
     {
@@ -245,7 +244,7 @@ void IconView::PaintEntry(SvTreeListEntry& rEntry, tools::Long nX, tools::Long n
         nLabelHeight += nItemHeight;
     }
 
-    int nLabelYPos = nY + nTempEntryHeight - nLabelHeight - nSpacing; // padding from bottom
+    int nLabelYPos = nY + nTempEntryHeight - nLabelHeight - m_nSpacing; // padding from bottom
     for (auto nCurItem : aTextItems)
     {
         aEntryPos.setY(nLabelYPos);
@@ -271,12 +270,12 @@ void IconView::PaintEntry(SvTreeListEntry& rEntry, tools::Long nX, tools::Long n
         // center horizontally
         aEntryPos.AdjustX((nTempEntryWidth - nItemWidth) / 2);
         // center vertically
-        int nImageAreaHeight = nTempEntryHeight - nSpacing * 2; // spacings from top, from bottom
+        int nImageAreaHeight = nTempEntryHeight - m_nSpacing * 2; // spacings from top, from bottom
         if (nLabelHeight > 0)
         {
-            nImageAreaHeight -= nLabelHeight + nSpacing; // spacing between icon and label
+            nImageAreaHeight -= nLabelHeight + m_nSpacing; // spacing between icon and label
         }
-        aEntryPos.AdjustY((nImageAreaHeight - nItemHeight) / 2 + nSpacing);
+        aEntryPos.AdjustY((nImageAreaHeight - nItemHeight) / 2 + m_nSpacing);
 
         rItem.Paint(aEntryPos, *this, rRenderContext, &rViewDataEntry, rEntry);
     }

vcl/source/window/builder.cxx

@@ -1418,6 +1418,10 @@ VclPtr<vcl::Window> VclBuilder::makeObject(vcl::Window *pParent, const OUString
         auto aColumnsIt = rMap.find(u"columns"_ustr);
         if (aColumnsIt != rMap.end())
             xBox->SetFixedColumnCount(aColumnsIt->second.toInt32());
+
+        auto aItemPaddingIt = rMap.find(u"item-padding"_ustr);
+        if (aItemPaddingIt != rMap.end())
+            xBox->SetSpacing(aItemPaddingIt->second.toInt32());
     }
     else if (name == "GtkTreeView")
     {