Workaround for zoom levels < 1 in eescxhema, with wxMSW version < 2.9

eeschema/libeditframe.cpp

@@ -389,7 +389,17 @@ int LIB_EDIT_FRAME::BestZoom()
     ii = wxRound( ( (double) dx / (double) size.x ) * (double) GetScreen()->m_ZoomScalar );
     jj = wxRound( ( (double) dy / (double) size.y ) * (double) GetScreen()->m_ZoomScalar );
 
-    return MAX( ii + 1, jj + 1 );
+    int bestzoom = MAX( ii + 1, jj + 1 );
+#if defined( __WINDOWS__ ) && !wxCHECK_VERSION(2, 9, 1)
+    /* This is a workaround: wxWidgets (wxMSW) before version 2.9 seems have
+     * problems with scale values < 1
+     * corresponding to values < GetScreen()->m_ZoomScalar
+     * So we keep bestzoom >= GetScreen()->m_ZoomScalar
+     */
+    if( bestzoom < GetScreen()->m_ZoomScalar )
+        bestzoom = GetScreen()->m_ZoomScalar;
+#endif
+    return bestzoom;
 }
 
 

eeschema/sch_screen.cpp

@@ -30,10 +30,25 @@
 /* Default EESchema zoom values. Limited to 17 values to keep a decent size
  * to menus
  */
+#if defined( __WINDOWS__ ) && !wxCHECK_VERSION(2, 9, 1)
+/* Please, note: wxWidgets (wxMSW) before version 2.9 seems have
+ * problems with scale values < 1
+ * because  scale value is SchematicZoomList[x] / 10
+ * ( in fact is SchematicZoomList[x] / m_ZoomScalar )
+ * do not use values smaller than 10 without testing them under wxWidgets versions < 2.9
+ * value like 0.5 seems work
+ */
+static int SchematicZoomList[] =
+{
+    5, 10, 15, 20, 30, 40, 60, 80, 120, 160, 230, 320, 480, 640, 800, 1280
+};
+
+#else
 static int SchematicZoomList[] =
 {
     5, 7, 10, 15, 20, 30, 40, 60, 80, 120, 160, 230, 320, 480, 640, 800, 1280
 };
+#endif
 
 #define SCHEMATIC_ZOOM_LIST_CNT  ( sizeof( SchematicZoomList ) / sizeof( int ) )
 #define MM_TO_SCH_UNITS 1000.0 / 25.4       //schematic internal unites are mils

eeschema/schframe.cpp

@@ -393,17 +393,28 @@ int SCH_EDIT_FRAME::BestZoom()
 {
     int    dx, dy;
     wxSize size;
-    double zoom;
 
     dx = GetScreen()->m_CurrentSheetDesc->m_Size.x;
     dy = GetScreen()->m_CurrentSheetDesc->m_Size.y;
 
     size = DrawPanel->GetClientSize();
-    zoom = MAX( (double) dx / (double) size.x, (double) dy / (double) size.y );
+    int ii = wxRound( (double) dx / size.x * (double) GetScreen()->m_ZoomScalar );
+    int jj = wxRound( (double) dx / size.x * (double) GetScreen()->m_ZoomScalar );
+    int bestzoom = MAX( ii, jj );
 
     GetScreen()->SetScrollCenterPosition( wxPoint( dx / 2, dy / 2 ) );
 
-    return wxRound( zoom * (double) GetScreen()->m_ZoomScalar );
+#if defined( __WINDOWS__ ) && !wxCHECK_VERSION(2, 9, 1)
+    /* This is a workaround: wxWidgets (wxMSW) before version 2.9 seems have
+     * problems with scale values < 1
+     * corresponding to values < GetScreen()->m_ZoomScalar
+     * So we keep bestzoom >= GetScreen()->m_ZoomScalar
+     */
+    if( bestzoom < GetScreen()->m_ZoomScalar )
+        bestzoom = GetScreen()->m_ZoomScalar;
+#endif
+
+    return bestzoom;
 }
 
 

eeschema/viewlib_frame.cpp

@@ -358,6 +358,16 @@ int LIB_VIEW_FRAME::BestZoom()
                     (double) GetScreen()->m_ZoomScalar );
     bestzoom = MAX( ii, jj ) + 1;
 
+#if defined( __WINDOWS__ ) && !wxCHECK_VERSION(2, 9, 1)
+    /* This is a workaround: wxWidgets (wxMSW) before version 2.9 seems have
+     * problems with scale values < 1
+     * corresponding to values < GetScreen()->m_ZoomScalar
+     * So we keep bestzoom >= GetScreen()->m_ZoomScalar
+     */
+    if( bestzoom < GetScreen()->m_ZoomScalar )
+        bestzoom = GetScreen()->m_ZoomScalar;
+#endif
+
     GetScreen()->SetScrollCenterPosition( BoundaryBox.Centre() );
 
     return bestzoom;