Add wxListBox::GetTopItem() and GetCountPerPage()

Implement these methods for all the major ports, add them to the widgets
sample and documentation.

Closes #17189.

docs/changes.txt

@@ -96,6 +96,7 @@ All (GUI):
 - Allow customizing window shown by wxBusyInfo.
 - Add wxAddRemoveCtrl.
 - Add wxAppProgressIndicator for MSW (Chaobin Zhang) and OS X (Tobias Taschner).
+- Add wxListBox::GetTopItem() and GetCountPerPage() (Andreas Falkenhahn).
 - Add wxTextEntry::ForceUpper().
 - Add wxTextEntryDialog::ForceUpper().
 - Add wxEVT_MAGNIFY mouse event (Joost Nieuwenhuijse).

include/wx/gtk/listbox.h

@@ -74,6 +74,8 @@ public:
 
     virtual void EnsureVisible(int n) wxOVERRIDE;
 
+    virtual int GetTopItem() const wxOVERRIDE;
+
     virtual void Update() wxOVERRIDE;
 
     static wxVisualAttributes

include/wx/listbox.h

@@ -72,6 +72,9 @@ public:
     // necessary
     virtual void EnsureVisible(int n);
 
+    virtual int GetTopItem() const { return wxNOT_FOUND; }
+    virtual int GetCountPerPage() const;
+
     // a combination of Append() and EnsureVisible(): appends the item to the
     // listbox and ensures that it is visible i.e. not scrolled out of view
     void AppendAndEnsureVisible(const wxString& s);
@@ -133,6 +136,8 @@ protected:
     // single selection mode on platforms other than MSW).
     void UpdateOldSelections();
 
+    wxCoord GetLineHeight() const;
+
 private:
     wxDECLARE_NO_COPY_CLASS(wxListBoxBase);
 };

include/wx/msw/listbox.h

@@ -95,6 +95,9 @@ public:
 
     virtual void EnsureVisible(int n);
 
+    virtual int GetTopItem() const;
+    virtual int GetCountPerPage() const;
+
     // ownerdrawn wxListBox and wxCheckListBox support
 #if wxUSE_OWNER_DRAWN
     // override base class virtuals

include/wx/osx/core/private.h

@@ -609,6 +609,7 @@ public:
     // display
 
     virtual void            ListScrollTo( unsigned int n ) = 0;
+    virtual int             ListGetTopItem() const = 0;
     virtual void            UpdateLine( unsigned int n, wxListWidgetColumn* col = NULL ) = 0;
     virtual void            UpdateLineToEnd( unsigned int n) = 0;
 

include/wx/osx/listbox.h

@@ -108,6 +108,8 @@ public:
 
     virtual void EnsureVisible(int n) wxOVERRIDE;
 
+    virtual int GetTopItem() const wxOVERRIDE;
+
     virtual wxVisualAttributes GetDefaultAttributes() const wxOVERRIDE
     {
         return GetClassDefaultAttributes(GetWindowVariant());

interface/wx/listbox.h

@@ -297,6 +297,25 @@ public:
      */
     virtual bool IsSorted() const;
 
+    /**
+        Return the number of items that can fit vertically in the visible area of
+        the listbox.
+
+        Returns -1 if the number of items per page couldn't be determined.
+
+        @since 3.1.0
+    */
+    int GetCountPerPage() const;
+
+    /**
+        Return the index of the topmost visible item.
+
+        Returns ::wxNOT_FOUND if the method is not implemented for the current
+        platform.
+
+        @since 3.1.0
+    */
+    int GetTopItem() const;
 
     // NOTE: Phoenix needs to see the implementation of pure virtuals so it
     // knows that this class is not abstract.

samples/widgets/listbox.cpp

@@ -69,7 +69,9 @@ enum
     ListboxPage_Listbox,
     ListboxPage_EnsureVisible,
     ListboxPage_EnsureVisibleText,
-    ListboxPage_ContainerTests
+    ListboxPage_ContainerTests,
+    ListboxPage_GetTopItem,
+    ListboxPage_GetCountPerPage
 };
 
 // ----------------------------------------------------------------------------
@@ -99,6 +101,8 @@ protected:
     void OnButtonAdd(wxCommandEvent& event);
     void OnButtonAddSeveral(wxCommandEvent& event);
     void OnButtonAddMany(wxCommandEvent& event);
+    void OnButtonTopItem(wxCommandEvent& event);
+    void OnButtonPageCount(wxCommandEvent& event);
 
     void OnListbox(wxCommandEvent& event);
     void OnListboxDClick(wxCommandEvent& event);
@@ -186,6 +190,8 @@ wxBEGIN_EVENT_TABLE(ListboxWidgetsPage, WidgetsPage)
     EVT_BUTTON(ListboxPage_AddSeveral, ListboxWidgetsPage::OnButtonAddSeveral)
     EVT_BUTTON(ListboxPage_AddMany, ListboxWidgetsPage::OnButtonAddMany)
     EVT_BUTTON(ListboxPage_ContainerTests, ItemContainerWidgetsPage::OnButtonTestItemContainer)
+    EVT_BUTTON(ListboxPage_GetTopItem, ListboxWidgetsPage::OnButtonTopItem)
+    EVT_BUTTON(ListboxPage_GetCountPerPage, ListboxWidgetsPage::OnButtonPageCount)
 
     EVT_TEXT_ENTER(ListboxPage_AddText, ListboxWidgetsPage::OnButtonAdd)
     EVT_TEXT_ENTER(ListboxPage_DeleteText, ListboxWidgetsPage::OnButtonDelete)
@@ -333,6 +339,12 @@ void ListboxWidgetsPage::CreateContent()
     btn = new wxButton(this, ListboxPage_Clear, wxT("&Clear"));
     sizerMiddle->Add(btn, 0, wxALL | wxGROW, 5);
 
+    btn = new wxButton(this, ListboxPage_GetTopItem, wxT("Get top item"));
+    sizerMiddle->Add(btn, 0, wxALL | wxGROW, 5);
+
+    btn = new wxButton(this, ListboxPage_GetCountPerPage, wxT("Get count per page"));
+    sizerMiddle->Add(btn, 0, wxALL | wxGROW, 5);
+
     btn = new wxButton(this, ListboxPage_ContainerTests, wxT("Run &tests"));
     sizerMiddle->Add(btn, 0, wxALL | wxGROW, 5);
 
@@ -514,6 +526,18 @@ void ListboxWidgetsPage::OnButtonClear(wxCommandEvent& WXUNUSED(event))
     m_lbox->Clear();
 }
 
+void ListboxWidgetsPage::OnButtonTopItem(wxCommandEvent& WXUNUSED(event))
+{
+    int item = m_lbox->GetTopItem();
+    wxLogMessage("Topmost visible item is: %d", item);
+}
+
+void ListboxWidgetsPage::OnButtonPageCount(wxCommandEvent& WXUNUSED(event))
+{
+    int count = m_lbox->GetCountPerPage();
+    wxLogMessage("%d items fit into this listbox.", count);
+}
+
 void ListboxWidgetsPage::OnButtonAdd(wxCommandEvent& WXUNUSED(event))
 {
     static unsigned int s_item = 0;

src/common/lboxcmn.cpp

@@ -33,6 +33,15 @@
     #include "wx/log.h"
 #endif
 
+// the spacing between the lines (in report mode)
+static const int LINE_SPACING = 0;
+
+#ifdef __WXGTK__
+static const int EXTRA_HEIGHT = 6;
+#else
+static const int EXTRA_HEIGHT = 4;
+#endif
+
 extern WXDLLEXPORT_DATA(const char) wxListBoxNameStr[] = "listBox";
 
 // ============================================================================
@@ -340,4 +349,23 @@ void wxListBoxBase::EnsureVisible(int WXUNUSED(n))
     // call SetFirstItem() but this is probably even more stupid)
 }
 
+wxCoord wxListBoxBase::GetLineHeight() const
+{
+    wxListBoxBase *self = wxConstCast(this, wxListBoxBase);
+
+    wxClientDC dc( self );
+    dc.SetFont( GetFont() );
+
+    wxCoord y;
+    dc.GetTextExtent(wxT("H"), NULL, &y);
+
+    y += EXTRA_HEIGHT;
+
+    return y + LINE_SPACING;
+}
+
+int wxListBoxBase::GetCountPerPage() const
+{
+    return GetClientSize().y / GetLineHeight();
+}
 #endif // wxUSE_LISTBOX

src/gtk/listbox.cpp

@@ -771,6 +771,24 @@ void wxListBox::EnsureVisible(int n)
     DoScrollToCell(n, 0.5, 0);
 }
 
+int wxListBox::GetTopItem() const
+{
+    int idx = wxNOT_FOUND;
+
+    GtkTreePath *start;
+    if ( gtk_tree_view_get_visible_range(m_treeview, &start, NULL) )
+    {
+        gint *ptr = gtk_tree_path_get_indices(start);
+
+        if ( ptr )
+            idx = *ptr;
+
+        gtk_tree_path_free(start);
+    }
+
+    return idx;
+}
+
 // ----------------------------------------------------------------------------
 // hittest
 // ----------------------------------------------------------------------------

src/msw/listbox.cpp

@@ -253,6 +253,22 @@ void wxListBox::EnsureVisible(int n)
     DoSetFirstItem(n - countVisible + 1);
 }
 
+int wxListBox::GetTopItem() const
+{
+    return SendMessage(GetHwnd(), LB_GETTOPINDEX, 0, 0);
+}
+
+int wxListBox::GetCountPerPage() const
+{
+    const LRESULT lineHeight = SendMessage(GetHwnd(), LB_GETITEMHEIGHT, 0, 0);
+    if ( lineHeight == LB_ERR || lineHeight == 0 )
+        return -1;
+
+    const RECT r = wxGetClientRect(GetHwnd());
+
+    return (r.bottom - r.top) / lineHeight;
+}
+
 void wxListBox::DoSetFirstItem(int N)
 {
     wxCHECK_RET( IsValid(N),

src/osx/cocoa/listbox.mm

@@ -129,6 +129,8 @@ public :
 
     virtual void            ListScrollTo( unsigned int n ) wxOVERRIDE ;
 
+    virtual int             ListGetTopItem() conswxOVERRIDE t;
+
     // accessing content
 
     virtual unsigned int    ListGetCount() const wxOVERRIDE ;
@@ -534,6 +536,13 @@ void wxListWidgetCocoaImpl::ListScrollTo( unsigned int n )
     [m_tableView scrollRowToVisible:n];
 }
 
+int wxListWidgetCocoaImpl::ListGetTopItem() const
+{
+     NSScrollView *scrollView = [m_tableView enclosingScrollView];
+     NSRect visibleRect = scrollView.contentView.visibleRect;
+     NSRange range = [m_tableView rowsInRect:visibleRect];
+     return range.location;
+}
 
 void wxListWidgetCocoaImpl::UpdateLine( unsigned int WXUNUSED(n), wxListWidgetColumn* WXUNUSED(col) )
 {

src/osx/listbox_osx.cpp

@@ -145,6 +145,11 @@ void wxListBox::EnsureVisible(int n)
     GetListPeer()->ListScrollTo( n );
 }
 
+int wxListBox::GetTopItem() const
+{
+    return GetListPeer()->ListGetTopItem();
+}
+
 void wxListBox::DoDeleteOneItem(unsigned int n)
 {
     wxCHECK_RET( IsValid(n), wxT("invalid index in wxListBox::Delete") );