Add wxListCtrl::IsVisible()

Allow checking if the given item is (at least partially) visible on
screen.

Closes https://github.com/wxWidgets/wxWidgets/pull/1444

Closes #9949.

include/wx/generic/listctrl.h

@@ -130,6 +130,7 @@ public:
     bool EndEditLabel(bool cancel);
 
     wxTextCtrl* GetEditControl() const;
+    bool IsVisible(long item) const wxOVERRIDE;
     void Edit( long item ) { EditLabel(item); }
 
     bool EnsureVisible( long item );

include/wx/listbase.h

@@ -400,6 +400,9 @@ public:
     bool InReportView() const { return HasFlag(wxLC_REPORT); }
     bool IsVirtual() const { return HasFlag(wxLC_VIRTUAL); }
 
+    // Check if the item is visible
+    virtual bool IsVisible(long WXUNUSED(item)) const { return false; }
+
     // Enable or disable beep when incremental match doesn't find any item.
     // Only implemented in the generic version currently.
     virtual void EnableBellOnNoMatch(bool WXUNUSED(on) = true) { }

include/wx/msw/listctrl.h

@@ -154,6 +154,9 @@ public:
     // Gets information about the item
     bool GetItem(wxListItem& info) const;
 
+    // Check if the item is visible
+    bool IsVisible(long item) const wxOVERRIDE;
+
     // Sets information about the item
     bool SetItem(wxListItem& info);
 

interface/wx/listctrl.h

@@ -1088,6 +1088,16 @@ public:
     */
     void SetImageList(wxImageList* imageList, int which);
 
+    /**
+        Check if the item is visible.
+
+        An item is considered visible if at least one pixel of it is present
+        on the screen.
+
+        @since 3.1.3
+    */
+    bool IsVisible(long item) const;
+
     /**
         Sets the data of an item.
 

samples/listctrl/listtest.cpp

@@ -151,6 +151,7 @@ wxBEGIN_EVENT_TABLE(MyFrame, wxFrame)
     EVT_MENU(LIST_TOGGLE_LINES, MyFrame::OnToggleLines)
     EVT_MENU(LIST_TOGGLE_HEADER, MyFrame::OnToggleHeader)
     EVT_MENU(LIST_TOGGLE_BELL, MyFrame::OnToggleBell)
+    EVT_MENU(LIST_CHECKVISIBILITY, MyFrame::OnCheckVisibility)
 #ifdef __WXOSX__
     EVT_MENU(LIST_MAC_USE_GENERIC, MyFrame::OnToggleMacUseGeneric)
 #endif // __WXOSX__
@@ -267,6 +268,7 @@ MyFrame::MyFrame(const wxString& title)
     menuList->AppendCheckItem(LIST_TOGGLE_HEADER, "Toggle &header\tCtrl-H");
     menuList->Check(LIST_TOGGLE_HEADER, true);
     menuList->AppendCheckItem(LIST_TOGGLE_BELL, "Toggle &bell on no match");
+    menuList->Append( LIST_CHECKVISIBILITY, "Check if lines 2 and 9 are visible" );
     menuList->AppendSeparator();
     menuList->AppendCheckItem(LIST_TOGGLE_CHECKBOXES,
                               "&Enable Checkboxes");
@@ -377,6 +379,18 @@ void MyFrame::OnToggleBell(wxCommandEvent& event)
     m_listCtrl->EnableBellOnNoMatch(event.IsChecked());
 }
 
+void MyFrame::OnCheckVisibility(wxCommandEvent& WXUNUSED(event))
+{
+    if ( m_listCtrl->IsVisible(2) )
+        wxLogMessage( "Line 2 is visible" );
+    else
+        wxLogMessage( "Line 2 is not visible" );
+    if ( m_listCtrl->IsVisible(9) )
+        wxLogMessage( "Line 9 is visible" );
+    else
+        wxLogMessage( "Line 9 is not visible" );
+}
+
 #ifdef __WXOSX__
 
 void MyFrame::OnToggleMacUseGeneric(wxCommandEvent& event)

samples/listctrl/listtest.h

@@ -117,7 +117,7 @@ protected:
     void OnSmallIconTextView(wxCommandEvent& event);
     void OnVirtualView(wxCommandEvent& event);
     void OnSmallVirtualView(wxCommandEvent& event);
-
+    void OnCheckVisibility(wxCommandEvent& event);
     void OnSetItemsCount(wxCommandEvent& event);
 
 
@@ -247,6 +247,6 @@ enum
 #ifdef __WXOSX__
     LIST_MAC_USE_GENERIC,
 #endif
-
+    LIST_CHECKVISIBILITY,
     LIST_CTRL                   = 1000
 };

src/generic/listctrl.cpp

@@ -151,6 +151,23 @@ wxListItemData::wxListItemData(wxListMainWindow *owner)
         m_rect = new wxRect;
 }
 
+// Check if the item is visible
+bool wxGenericListCtrl::IsVisible(long item) const
+{
+    wxRect itemRect;
+    GetItemRect( item, itemRect );
+    const wxRect clientRect = GetClientRect();
+    bool visible = clientRect.Intersects( itemRect );
+    if ( visible && m_headerWin )
+    {
+        wxRect headerRect = m_headerWin->GetClientRect();
+        // take into account the +1 added in GetSubItemRect()
+        headerRect.height++;
+        visible = itemRect.GetBottom() > headerRect.GetBottom();
+    }
+    return visible;
+}
+
 void wxListItemData::SetItem( const wxListItem &info )
 {
     if ( info.m_mask & wxLIST_MASK_TEXT )

src/msw/listctrl.cpp

@@ -67,6 +67,10 @@
     #define NO_ITEM (-1)
 #endif
 
+#ifndef LVM_ISITEMVISIBLE
+    #define LVM_ISITEMVISIBLE (LVM_FIRST + 182)
+#endif
+
 // ----------------------------------------------------------------------------
 // private functions
 // ----------------------------------------------------------------------------
@@ -880,6 +884,25 @@ bool wxListCtrl::GetItem(wxListItem& info) const
     return success;
 }
 
+// Check if the item is visible
+bool wxListCtrl::IsVisible(long item) const
+{
+    bool result = ::SendMessage( GetHwnd(), LVM_ISITEMVISIBLE, (WPARAM) item, 0 ) != 0;
+    if ( result )
+    {
+        HWND hwndHdr = ListView_GetHeader(GetHwnd());
+        wxRect itemRect;
+        RECT headerRect;
+        if ( Header_GetItemRect( hwndHdr, 0, &headerRect ) )
+        {
+            GetItemRect( item, itemRect );
+            wxRect rectHeader = wxRectFromRECT( headerRect );
+            result = itemRect.GetBottom() > rectHeader.GetBottom();
+        }
+    }
+    return result;
+}
+
 // Sets information about the item
 bool wxListCtrl::SetItem(wxListItem& info)
 {