Grid: Add row/column stretch implementation

Also add a basic test case for stretch behaviour.

simgear/canvas/layout/GridLayout.cxx

@@ -301,17 +301,62 @@ void GridLayout::setDimensions(const SGVec2i& dim)
     invalidate();
 }
 
+//----------------------------------------------------------------------------
 size_t GridLayout::numRows() const
 {
     return _dimensions.y();
 }
 
+//----------------------------------------------------------------------------
 size_t GridLayout::numColumns() const
 {
     return _dimensions.x();
 }
 
 
+//----------------------------------------------------------------------------
+void GridLayout::setRowStretch(size_t index, int stretch)
+{
+    if (index >= _dimensions.y()) {
+        throw sg_range_exception("GridLayout::setRowStretch: invalid row");
+    }
+
+    if (stretch < 0) {
+        throw sg_range_exception("GridLayout: negative stretch values are forbidden");
+    }
+
+    // becuase we lazily update the rows data, we'd have nowhere to store the
+    // new stretch value, so actively resize it now.
+    if (index >= _rows.size()) {
+        _rows.resize(_dimensions.y());
+    }
+
+    _rows[index].stretch = stretch;
+    invalidate();
+}
+
+//----------------------------------------------------------------------------
+
+void GridLayout::setColumnStretch(size_t index, int stretch)
+{
+    if (index >= _dimensions.x()) {
+        throw sg_range_exception("GridLayout::setColumnStretch: invalid column");
+    }
+
+    if (stretch < 0) {
+        throw sg_range_exception("GridLayout: negative stretch values are forbidden");
+    }
+
+    // becuase we lazily update the columns data, we'd have nowhere to store the
+    // new stretch value, so actively resize it now.
+    if (index >= _columns.size()) {
+        _columns.resize(_dimensions.x());
+    }
+
+    _columns[index].stretch = stretch;
+    invalidate();
+}
+
 //----------------------------------------------------------------------------
 void GridLayout::updateSizeHints() const
 {

simgear/canvas/layout/GridLayout.hxx

@@ -26,21 +26,21 @@ public:
 
     void addItem(const LayoutItemRef& item, int column, int row, int colSpan = 1, int rowSpan = 1);
 
-    virtual void addItem(const LayoutItemRef& item);
+    void addItem(const LayoutItemRef& item) override;
 
-    virtual size_t count() const;
-    virtual LayoutItemRef itemAt(size_t index);
-    virtual LayoutItemRef takeAt(size_t index);
-    virtual void clear();
+    size_t count() const override;
+    LayoutItemRef itemAt(size_t index) override;
+    LayoutItemRef takeAt(size_t index) override;
+    void clear() override;
 
-    virtual void setSpacing(int spacing);
-    virtual int spacing() const;
+    void setSpacing(int spacing) override;
+    int spacing() const override;
 
     void invalidate() override;
 
-    virtual bool hasHeightForWidth() const;
+    bool hasHeightForWidth() const override;
 
-    virtual void setCanvas(const CanvasWeakPtr& canvas);
+    void setCanvas(const CanvasWeakPtr& canvas) override;
 
     void setRowStretch(size_t index, int stretch);
     void setColumnStretch(size_t index, int stretch);

simgear/canvas/layout/canvas_layout_test.cxx

@@ -807,3 +807,42 @@ BOOST_AUTO_TEST_CASE(gridlayout_min_size_layout)
     BOOST_CHECK_EQUAL(w2->geometry(), SGRecti(89, 18, 109, 78));
     BOOST_CHECK_EQUAL(w4->geometry(), SGRecti(0, 100, 198, 46));
 }
+
+//------------------------------------------------------------------------------
+BOOST_AUTO_TEST_CASE(gridlayout_stretch)
+{
+    sc::GridLayoutRef grid(new sc::GridLayout);
+    grid->setSpacing(4);
+    grid->setDimensions({3, 3});
+
+    TestWidgetRef w1(new TestWidget(SGVec2i(16, 16),
+                                    SGVec2i(32, 32),
+                                    SGVec2i(9999, 9999))),
+        w2(new TestWidget(*w1)),
+        w3(new TestWidget(*w1)),
+        w4(new TestWidget(*w1)),
+        w5(new TestWidget(*w1));
+
+
+    grid->setColumnStretch(1, 1);
+    grid->setColumnStretch(2, 2);
+
+    grid->setRowStretch(0, 1);
+    grid->setRowStretch(1, 4);
+    grid->setRowStretch(2, 1);
+
+    w1->setGridSpan({1, 2});
+
+    grid->addItem(w1);
+    grid->addItem(w2, 1, 1);
+    grid->addItem(w3, 2, 1);
+    grid->addItem(w4, 0, 2, 2 /* col span */, 1);
+    grid->addItem(w5, 2, 0);
+
+    grid->setGeometry(SGRecti(0, 0, 248, 224));
+
+    BOOST_CHECK_EQUAL(w1->geometry(), SGRecti(0, 0, 32, 168));
+    BOOST_CHECK_EQUAL(w2->geometry(), SGRecti(36, 56, 80, 112));
+    BOOST_CHECK_EQUAL(w4->geometry(), SGRecti(0, 172, 116, 52));
+    BOOST_CHECK_EQUAL(w5->geometry(), SGRecti(120, 0, 128, 52));
+}