Implement drawing under overlay terrains (use ALT)

changelog

@@ -33,6 +33,7 @@ Version 1.5.0-svn:
    * Fixed not working "Update transition" and make "Delay transition update"
      directly trigger an update when toggled off.
    * add-ons can now make their custom terrains available in the editor
+   * Draw base terrain under an overlay when ALT is pressed
  * game engine
    * Implemented lazy loading for unit_types
  * multiplayer:

src/editor/editor.cpp

@@ -412,6 +412,11 @@ void map_editor::left_click(const gamemap::location hex_clicked) {
 		}
 		l_button_held_func_ = NONE;
 	}
+	else if ( (key_[SDLK_RALT] || key_[SDLK_LALT]) && l_button_func_ == DRAW) {
+		reset_mouseover_overlay();
+		draw_on_mouseover_hexes(palette_.selected_fg_terrain(), true);
+		l_button_held_func_ = DRAW_BASE_TERRAIN;
+	}
 	else if (selected_hexes_.find(hex_clicked) != selected_hexes_.end()) {
 		l_button_held_func_ = MOVE_SELECTION;
 		selection_move_start_ = hex_clicked;
@@ -1181,6 +1186,10 @@ void map_editor::left_button_down(const int mousex, const int mousey) {
 		reset_mouseover_overlay();
 		draw_on_mouseover_hexes(palette_.selected_fg_terrain());
 	}
+	else if (l_button_held_func_ == DRAW_BASE_TERRAIN && mouse_moved_) {
+		reset_mouseover_overlay();
+		draw_on_mouseover_hexes(palette_.selected_fg_terrain(), true);
+	}
 	else if (l_button_held_func_ == MOVE_SELECTION && mouse_moved_) {
 		reset_mouseover_overlay();
 		//(*it-selection_move_start_) + hex
@@ -1196,16 +1205,16 @@ void map_editor::left_button_down(const int mousex, const int mousey) {
 	}
 }
 
-void map_editor::draw_on_mouseover_hexes(const t_translation::t_terrain terrain) {
+void map_editor::draw_on_mouseover_hexes(const t_translation::t_terrain terrain, const bool base_only) {
 	if(map_.on_board(selected_hex_, true)) {
 		std::vector<gamemap::location> hexes =
 			get_tiles(map_, selected_hex_, brush_.selected_brush_size());
-		draw_terrain(terrain, hexes);
+		draw_terrain(terrain, hexes, base_only);
 	}
 }
 
 void map_editor::draw_terrain(const t_translation::t_terrain terrain,
-		const std::vector<gamemap::location> &hexes)
+                              const std::vector<gamemap::location> &hexes, const bool base_only)
 {
 	map_undo_action undo_action;
 	
@@ -1214,12 +1223,16 @@ void map_editor::draw_terrain(const t_translation::t_terrain terrain,
 		const t_translation::t_terrain old_terrain = map_.get_terrain(*it);
 		if(terrain != old_terrain) {
 			undo_action.add_terrain(old_terrain, terrain, *it);
-            if (terrain.base == t_translation::NO_LAYER) {
-                map_.set_overlay(*it, terrain);
-            }
-            else {
-                map_.set_terrain(*it, terrain);
-            }
+			if (terrain.base == t_translation::NO_LAYER) {
+				map_.set_overlay(*it, terrain);
+			}
+			else if (base_only) {
+				map_.set_base(*it, terrain);
+			}
+			else {
+				map_.set_terrain(*it, terrain);
+			}
+
 			// always rebuild localy to show the drawing progress
 			gui_.rebuild_terrain(*it);
 			gui_.invalidate(*it);
@@ -1262,7 +1275,12 @@ void map_editor::right_button_down(const int /*mousex*/, const int /*mousey*/) {
 	// Draw with the background terrain on rightclick,
 	// no matter what operations are wanted with the left button.
 	//! @todo TODO evaluate if this is what is the smartest thing to do.
-	draw_on_mouseover_hexes(palette_.selected_bg_terrain());
+	if (DRAW_BASE_TERRAIN) {
+		draw_on_mouseover_hexes(palette_.selected_bg_terrain(), true);
+	}
+	else {
+		draw_on_mouseover_hexes(palette_.selected_bg_terrain());
+	}
 }
 
 void map_editor::middle_button_down(const int mousex, const int mousey) {

src/editor/editor.hpp

@@ -155,7 +155,7 @@ public:
 
 private:
 	//! What to perform while the left button is held down.
-	enum LEFT_BUTTON_HELD_FUNC {DRAW_TERRAIN, ADD_SELECTION, REMOVE_SELECTION,
+	enum LEFT_BUTTON_HELD_FUNC {DRAW_TERRAIN, DRAW_BASE_TERRAIN, ADD_SELECTION, REMOVE_SELECTION,
 								MOVE_SELECTION, NONE};
 
 	//! What to perform on a left button click.
@@ -205,7 +205,7 @@ private:
 	//! Draw terrain at a location. The operation is saved in the undo
 	//! stack. Update the map to reflect the change.
 	void draw_terrain(const t_translation::t_terrain terrain,
-					  const std::vector<gamemap::location> &hexes);
+					  const std::vector<gamemap::location> &hexes, const bool base_only);
 
 	//! Re-set the labels for the starting positions of the
 	//! players. Should be called when the terrain has changed, which
@@ -272,7 +272,7 @@ private:
 
 	//! Draw the terrain on the hexes the mouse is over, taking account
 	//! for brush size.
-	void draw_on_mouseover_hexes(const t_translation::t_terrain t);
+	void draw_on_mouseover_hexes(const t_translation::t_terrain t, const bool base_only = false);
 
 	// Load the tooltips for each button
 	void load_tooltips(void);