Add a new offsetted drawing method.

The code is mainly copy pasted from the current drawing code, but adds
some helpers as well.

The code is used to experiment with a different approach of the
implementation of a listbox.

src/gui/widgets/container.cpp

@@ -124,6 +124,17 @@ void tcontainer_::impl_draw_children(surface& frame_buffer)
 	grid_.draw_children(frame_buffer);
 }
 
+void tcontainer_::impl_draw_children(
+		  surface& frame_buffer
+		, int x_offset
+		, int y_offset)
+{
+	assert(get_visible() == twidget::VISIBLE
+			&& grid_.get_visible() == twidget::VISIBLE);
+
+	grid_.draw_children(frame_buffer, x_offset, y_offset);
+}
+
 void tcontainer_::layout_children()
 {
 	grid_.layout_children();

src/gui/widgets/container.hpp

@@ -107,6 +107,7 @@ public:
 
 	/** Inherited from twidget. */
 	void impl_draw_children(surface& frame_buffer);
+	void impl_draw_children(surface& frame_buffer, int x_offset, int y_offset);
 
 protected:
 

src/gui/widgets/control.cpp

@@ -335,6 +335,21 @@ void tcontrol::impl_draw_background(surface& frame_buffer)
 	canvas(get_state()).blit(frame_buffer, get_rect());
 }
 
+void tcontrol::impl_draw_background(
+		  surface& frame_buffer
+		, int x_offset
+		, int y_offset)
+{
+	DBG_GUI_D << LOG_HEADER
+			<< " label '" << debug_truncate(label_)
+			<< "' size " << get_rect()
+			<< ".\n";
+
+	canvas(get_state()).blit(
+			  frame_buffer
+			, calculate_blitting_rectangle(x_offset, y_offset));
+}
+
 tpoint tcontrol::get_best_text_size(
 		  const tpoint& minimum_size
 		, const tpoint& maximum_size) const

src/gui/widgets/control.hpp

@@ -318,9 +318,19 @@ public:
 protected:
 	/** Inherited from twidget. */
 	void impl_draw_background(surface& frame_buffer);
+	void impl_draw_background(
+			  surface& frame_buffer
+			, int x_offset
+			, int y_offset);
 
 	/** Inherited from twidget. */
 	void impl_draw_foreground(surface& /*frame_buffer*/) { /* do nothing */ }
+	void impl_draw_foreground(
+			  surface& /*frame_buffer*/
+			, int /*x_offset*/
+			, int /*y_offset*/)
+	{ /* do nothing */ }
+
 private:
 
 	/**

src/gui/widgets/generator.hpp

@@ -259,6 +259,10 @@ public:
 
 	/** Inherited from twidget. */
 	virtual void impl_draw_children(surface& frame_buffer) = 0;
+	virtual void impl_draw_children(
+			  surface& frame_buffer
+			, int x_offset
+			, int y_offset) = 0;
 
 protected:
 

src/gui/widgets/generator_private.hpp

@@ -811,6 +811,18 @@ public:
 		}
 	}
 
+	/** Inherited from tgenerator_. */
+	void impl_draw_children(surface& frame_buffer, int x_offset, int y_offset)
+	{
+		assert(this->get_visible() == twidget::VISIBLE);
+
+		foreach(titem* item, items_) {
+			if(item->grid.get_visible() == twidget::VISIBLE && item->shown) {
+				item->grid.draw_children(frame_buffer, x_offset, y_offset);
+			}
+		}
+	}
+
 	/** Inherited from tgenerator_. */
 	void child_populate_dirty_list(twindow& caller,
 			const std::vector<twidget*>& call_stack)

src/gui/widgets/grid.cpp

@@ -956,6 +956,45 @@ void tgrid::impl_draw_children(surface& frame_buffer)
 	}
 }
 
+void tgrid::impl_draw_children(
+		  surface& frame_buffer
+		, int x_offset
+		, int y_offset)
+{
+	/*
+	 * The call to SDL_PumpEvents seems a bit like black magic.
+	 * With the call the resizing doesn't seem to lose resize events.
+	 * But when added the queue still only contains one resize event and the
+	 * internal SDL queue doesn't seem to overflow (rarely more than 50 pending
+	 * events).
+	 * Without the call when resizing larger a black area of remains, this is
+	 * the area not used for resizing the screen, this call `fixes' that.
+	 */
+	SDL_PumpEvents();
+
+	assert(get_visible() == twidget::VISIBLE);
+	set_dirty(false);
+
+	foreach(tchild& child, children_) {
+
+		twidget* widget = child.widget();
+		assert(widget);
+
+		if(widget->get_visible() != twidget::VISIBLE) {
+			continue;
+		}
+
+		if(widget->get_drawing_action() == twidget::NOT_DRAWN) {
+			continue;
+		}
+
+		widget->draw_background(frame_buffer, x_offset, y_offset);
+		widget->draw_children(frame_buffer, x_offset, y_offset);
+		widget->draw_foreground(frame_buffer, x_offset, y_offset);
+		widget->set_dirty(false);
+	}
+}
+
 unsigned tgrid_implementation::row_request_reduce_height(tgrid& grid,
 		const unsigned row, const unsigned maximum_height)
 {

src/gui/widgets/grid.hpp

@@ -430,6 +430,7 @@ private:
 
 	/** Inherited from twidget. */
 	void impl_draw_children(surface& frame_buffer);
+	void impl_draw_children(surface& frame_buffer, int x_offset, int y_offset);
 
 };
 

src/gui/widgets/minimap.cpp

@@ -232,6 +232,31 @@ void tminimap::impl_draw_background(surface& frame_buffer)
 	}
 }
 
+void tminimap::impl_draw_background(
+		  surface& frame_buffer
+		, int x_offset
+		, int y_offset)
+{
+	if (!terrain_) return;
+	assert(terrain_);
+
+	DBG_GUI_D << LOG_HEADER
+			<< " size " << calculate_blitting_rectangle(x_offset, y_offset)
+			<< ".\n";
+
+	if(map_data_.empty()) {
+		return;
+	}
+
+	SDL_Rect rect = calculate_blitting_rectangle(x_offset, y_offset);
+	assert(rect.w > 0 && rect.h > 0);
+
+	const ::surface surf = get_image(rect.w, rect.h);
+	if(surf) {
+		sdl_blit(surf, NULL, frame_buffer, &rect);
+	}
+}
+
 const std::string& tminimap::get_control_type() const
 {
 	static const std::string type = "minimap";

src/gui/widgets/minimap.hpp

@@ -87,6 +87,10 @@ private:
 
 	/** Inherited from tcontrol. */
 	void impl_draw_background(surface& frame_buffer);
+	void impl_draw_background(
+			  surface& frame_buffer
+			, int x_offset
+			, int y_offset);
 
 	/** Inherited from tcontrol. */
 	const std::string& get_control_type() const;

src/gui/widgets/multi_page.hpp

@@ -160,6 +160,10 @@ private:
 	 * Since we're always empty the draw does nothing.
 	 */
 	void impl_draw_background(surface& /*frame_buffer*/) {}
+	void impl_draw_background(
+			  surface& /*frame_buffer*/
+			, int /*x_offset*/
+			, int /*y_offset*/) {}
 
 	/** Inherited from tcontrol. */
 	const std::string& get_control_type() const;

src/gui/widgets/panel.cpp

@@ -55,11 +55,35 @@ void tpanel::impl_draw_background(surface& frame_buffer)
 	canvas(0).blit(frame_buffer, get_rect());
 }
 
+void tpanel::impl_draw_background(
+		  surface& frame_buffer
+		, int x_offset
+		, int y_offset)
+{
+	DBG_GUI_D << LOG_HEADER
+			<< " size " << get_rect()
+			<< ".\n";
+
+	canvas(0).blit(
+			  frame_buffer
+			, calculate_blitting_rectangle(x_offset, y_offset));
+}
+
 void tpanel::impl_draw_foreground(surface& frame_buffer)
 {
 	canvas(1).blit(frame_buffer, get_rect());
 }
 
+void tpanel::impl_draw_foreground(
+		  surface& frame_buffer
+		, int x_offset
+		, int y_offset)
+{
+	canvas(1).blit(
+			  frame_buffer
+			, calculate_blitting_rectangle(x_offset, y_offset));
+}
+
 tpoint tpanel::border_space() const
 {
 	boost::intrusive_ptr<const tpanel_definition::tresolution> conf =

src/gui/widgets/panel.hpp

@@ -61,9 +61,17 @@ private:
 
 	/** Inherited from tcontrol. */
 	void impl_draw_background(surface& frame_buffer);
+	void impl_draw_background(
+			  surface& frame_buffer
+			, int x_offset
+			, int y_offset);
 
 	/** Inherited from tcontrol. */
 	void impl_draw_foreground(surface& frame_buffer);
+	void impl_draw_foreground(
+			  surface& frame_buffer
+			, int x_offset
+			, int y_offset);
 
 	/** Inherited from tcontrol. */
 	const std::string& get_control_type() const;

src/gui/widgets/scrollbar_container.cpp

@@ -758,6 +758,20 @@ void tscrollbar_container::impl_draw_children(surface& frame_buffer)
 	content_grid_->draw_children(frame_buffer);
 }
 
+void tscrollbar_container::impl_draw_children(
+		  surface& frame_buffer
+		, int x_offset
+		, int y_offset)
+{
+	assert(get_visible() == twidget::VISIBLE
+			&& content_grid_->get_visible() == twidget::VISIBLE);
+
+	// Inherited.
+	tcontainer_::impl_draw_children(frame_buffer, x_offset, y_offset);
+
+	content_grid_->draw_children(frame_buffer, x_offset, y_offset);
+}
+
 void tscrollbar_container::layout_children()
 {
 	// Inherited.

src/gui/widgets/scrollbar_container.hpp

@@ -455,6 +455,7 @@ private:
 
 	/** Inherited from tcontainer_. */
 	void impl_draw_children(surface& frame_buffer);
+	void impl_draw_children(surface& frame_buffer, int x_offset, int y_offset);
 
 	/** Inherited from tcontainer_. */
 	void child_populate_dirty_list(twindow& caller,

src/gui/widgets/spacer.hpp

@@ -78,6 +78,10 @@ private:
 	 * Since we're always empty the draw does nothing.
 	 */
 	void impl_draw_background(surface& /*frame_buffer*/) {}
+	void impl_draw_background(
+			  surface& /*frame_buffer*/
+			, int /*x_offset*/
+			, int /*y_offset*/) {}
 
 	/** Inherited from tcontrol. */
 	const std::string& get_control_type() const;

src/gui/widgets/toggle_panel.hpp

@@ -160,6 +160,14 @@ private:
 		tcontrol::impl_draw_background(frame_buffer);
 	}
 
+	/** Inherited from tpanel. */
+	void impl_draw_background(surface& frame_buffer, int x_offset, int y_offset)
+	{
+		// We don't have a fore and background and need to draw depending on
+		// our state, like a control. So we use the controls drawing method.
+		tcontrol::impl_draw_background(frame_buffer, x_offset, y_offset);
+	}
+
 	/** Inherited from tpanel. */
 	void impl_draw_foreground(surface& frame_buffer)
 	{
@@ -168,6 +176,14 @@ private:
 		tcontrol::impl_draw_foreground(frame_buffer);
 	}
 
+	/** Inherited from tpanel. */
+	void impl_draw_foreground(surface& frame_buffer, int x_offset, int y_offset)
+	{
+		// We don't have a fore and background and need to draw depending on
+		// our state, like a control. So we use the controls drawing method.
+		tcontrol::impl_draw_foreground(frame_buffer, x_offset, y_offset);
+	}
+
 
 	/** Inherited from tpanel. */
 	const std::string& get_control_type() const;

src/gui/widgets/tree_view_node.cpp

@@ -496,6 +496,22 @@ void ttree_view_node::impl_draw_children(surface& frame_buffer)
 	}
 }
 
+void ttree_view_node::impl_draw_children(
+		  surface& frame_buffer
+		, int x_offset
+		, int y_offset)
+{
+	grid_.draw_children(frame_buffer, x_offset, y_offset);
+
+	if(is_folded()) {
+		return;
+	}
+
+	foreach(ttree_view_node& node, children_) {
+		node.impl_draw_children(frame_buffer, x_offset, y_offset);
+	}
+}
+
 void ttree_view_node::signal_handler_left_button_click(
 		const event::tevent event)
 {

src/gui/widgets/tree_view_node.hpp

@@ -251,6 +251,7 @@ private:
 	void set_visible_area(const SDL_Rect& area);
 
 	void impl_draw_children(surface& frame_buffer);
+	void impl_draw_children(surface& frame_buffer, int x_offset, int y_offset);
 
 	// FIXME rename to icon
 	void signal_handler_left_button_click(const event::tevent event);

src/gui/widgets/widget.cpp

@@ -251,6 +251,26 @@ void twidget::set_visible_area(const SDL_Rect& area)
 	}
 }
 
+SDL_Rect twidget::calculate_blitting_rectangle(
+		  const int x_offset
+		, const int y_offset)
+{
+	SDL_Rect result = get_rect();
+	result.x += x_offset;
+	result.y += y_offset;
+	return result;
+}
+
+SDL_Rect twidget::calculate_clipping_rectangle(
+		  const int x_offset
+		, const int y_offset)
+{
+	SDL_Rect result = clip_rect_;
+	result.x += x_offset;
+	result.y += y_offset;
+	return result;
+}
+
 void twidget::draw_background(surface& frame_buffer)
 {
 	assert(visible_ == VISIBLE);
@@ -265,6 +285,23 @@ void twidget::draw_background(surface& frame_buffer)
 	}
 }
 
+void twidget::draw_background(surface& frame_buffer, int x_offset, int y_offset)
+{
+	assert(visible_ == VISIBLE);
+
+	if(drawing_action_ == PARTLY_DRAWN) {
+		const SDL_Rect clipping_rectangle =
+				calculate_clipping_rectangle(x_offset, y_offset);
+
+		clip_rect_setter clip(frame_buffer, &clipping_rectangle);
+		draw_debug_border(frame_buffer, x_offset, y_offset);
+		impl_draw_background(frame_buffer, x_offset, y_offset);
+	} else {
+		draw_debug_border(frame_buffer, x_offset, y_offset);
+		impl_draw_background(frame_buffer, x_offset, y_offset);
+	}
+}
+
 void twidget::draw_children(surface& frame_buffer)
 {
 	assert(visible_ == VISIBLE);
@@ -277,6 +314,21 @@ void twidget::draw_children(surface& frame_buffer)
 	}
 }
 
+void twidget::draw_children(surface& frame_buffer, int x_offset, int y_offset)
+{
+	assert(visible_ == VISIBLE);
+
+	if(drawing_action_ == PARTLY_DRAWN) {
+		const SDL_Rect clipping_rectangle =
+				calculate_clipping_rectangle(x_offset, y_offset);
+
+		clip_rect_setter clip(frame_buffer, &clipping_rectangle);
+		impl_draw_children(frame_buffer, x_offset, y_offset);
+	} else {
+		impl_draw_children(frame_buffer, x_offset, y_offset);
+	}
+}
+
 void twidget::draw_foreground(surface& frame_buffer)
 {
 	assert(visible_ == VISIBLE);
@@ -289,6 +341,21 @@ void twidget::draw_foreground(surface& frame_buffer)
 	}
 }
 
+void twidget::draw_foreground(surface& frame_buffer, int x_offset, int y_offset)
+{
+	assert(visible_ == VISIBLE);
+
+	if(drawing_action_ == PARTLY_DRAWN) {
+		const SDL_Rect clipping_rectangle =
+				calculate_clipping_rectangle(x_offset, y_offset);
+
+		clip_rect_setter clip(frame_buffer, &clipping_rectangle);
+		impl_draw_foreground(frame_buffer, x_offset, y_offset);
+	} else {
+		impl_draw_foreground(frame_buffer, x_offset, y_offset);
+	}
+}
+
 #ifndef LOW_MEM
 void twidget::draw_debug_border(surface& frame_buffer)
 {
@@ -310,6 +377,31 @@ void twidget::draw_debug_border(surface& frame_buffer)
 			assert(false);
 	}
 }
+
+void twidget::draw_debug_border(
+		  surface& frame_buffer
+		, int x_offset
+		, int y_offset)
+{
+	SDL_Rect r = drawing_action_ == PARTLY_DRAWN
+		? calculate_clipping_rectangle(x_offset, y_offset)
+		: calculate_blitting_rectangle(x_offset, y_offset);
+
+	switch(debug_border_mode_) {
+		case 0:
+			/* DO NOTHING */
+			break;
+		case 1:
+			draw_rectangle(r.x, r.y, r.w, r.h
+					, debug_border_color_, frame_buffer);
+			break;
+		case 2:
+			sdl_fill_rect(frame_buffer, &r, debug_border_color_);
+			break;
+		default:
+			assert(false);
+	}
+}
 #endif
 
 bool twidget::is_at(const tpoint& coordinate, const bool must_be_active) const

src/gui/widgets/widget.hpp

@@ -452,6 +452,37 @@ public:
 	}
 #endif
 
+	/**
+	 * Calculates the blitting rectangle of the widget.
+	 *
+	 * The blitting rectangle is to entire widget rectangle, but offsetted for
+	 * drawing position.
+	 *
+	 * @param x_offset            The x offset when drawn.
+	 * @param y_offset            The y offset when drawn.
+	 *
+	 * @returns                   The drawing rectangle.
+	 */
+	SDL_Rect calculate_blitting_rectangle(
+			  const int x_offset
+			, const int y_offset);
+
+	/**
+	 * Calculates the clipping rectangle of the widget.
+	 *
+	 * The clipping rectangle is used then the @ref drawing_action_ is
+	 * @ref PARTLY_DRAWN. Since the drawing can be offsetted it also needs
+	 * offset paramters.
+	 *
+	 * @param x_offset            The x offset when drawn.
+	 * @param y_offset            The y offset when drawn.
+	 *
+	 * @returns                   The clipping rectangle.
+	 */
+	SDL_Rect calculate_clipping_rectangle(
+			  const int x_offset
+			, const int y_offset);
+
 	/**
 	 * Draws the background of a widget.
 	 *
@@ -459,8 +490,11 @@ public:
 	 * this function.
 	 *
 	 * @param frame_buffer        The surface to draw upon.
+	 * @param x_offset            The x offset in the @p frame_buffer to draw.
+	 * @param y_offset            The y offset in the @p frame_buffer to draw.
 	 */
 	void draw_background(surface& frame_buffer);
+	void draw_background(surface& frame_buffer, int x_offset, int y_offset);
 
 	/**
 	 * Draws the children of a widget.
@@ -471,8 +505,11 @@ public:
 	 * this function.
 	 *
 	 * @param frame_buffer        The surface to draw upon.
+	 * @param x_offset            The x offset in the @p frame_buffer to draw.
+	 * @param y_offset            The y offset in the @p frame_buffer to draw.
 	 */
 	void draw_children(surface& frame_buffer);
+	void draw_children(surface& frame_buffer, int x_offset, int y_offset);
 
 	/**
 	 * Draws the foreground of the widgt.
@@ -484,8 +521,11 @@ public:
 	 * this function.
 	 *
 	 * @param frame_buffer        The surface to draw upon.
+	 * @param x_offset            The x offset in the @p frame_buffer to draw.
+	 * @param y_offset            The y offset in the @p frame_buffer to draw.
 	 */
 	void draw_foreground(surface& frame_buffer);
+	void draw_foreground(surface& frame_buffer, int x_offset, int y_offset);
 
 	/**
 	 * Allows a widget to update its children.
@@ -638,8 +678,10 @@ private:
 	unsigned debug_border_color_;
 
 	void draw_debug_border(surface& frame_buffer);
+	void draw_debug_border(surface& frame_buffer, int x_offset, int y_offset);
 #else
 	void draw_debug_border(surface&) {}
+	void draw_debug_border(surface&, int, int) {}
 #endif
 
 #ifdef DEBUG_WINDOW_LAYOUT_GRAPHS
@@ -654,12 +696,30 @@ private:
 
 	/** See draw_background(). */
 	virtual void impl_draw_background(surface& /*frame_buffer*/) {}
+	virtual void impl_draw_background(
+			  surface& /*frame_buffer*/
+			, int /*x_offset*/
+			, int /*y_offset*/)
+	{
+	}
 
 	/** See draw_children. */
 	virtual void impl_draw_children(surface& /*frame_buffer*/) {}
+	virtual void impl_draw_children(
+			surface& /*frame_buffer*/
+			, int /*x_offset*/
+			, int /*y_offset*/)
+	{
+	}
 
 	/** See draw_foreground. */
 	virtual void impl_draw_foreground(surface& /*frame_buffer*/) {}
+	virtual void impl_draw_foreground(
+			  surface& /*frame_buffer*/
+			, int /*x_offset*/
+			, int /*y_offset*/)
+	{
+	}
 
 	/** (Will be) inherited from event::tdispatcher. */
 	virtual bool is_at(const tpoint& coordinate) const

src/gui/widgets/window.cpp

@@ -693,7 +693,14 @@ void twindow::draw()
 
 		// Now find the widgets that are dirty.
 		std::vector<twidget*> call_stack;
-		populate_dirty_list(*this, call_stack);
+		if(!new_widgets) {
+			populate_dirty_list(*this, call_stack);
+		} else {
+			/* Force to update and redraw the entire screen */
+			dirty_list_.clear();
+			dirty_list_.push_back(std::vector<twidget*>(1, this));
+			update_rect(screen_area());
+		}
 	}
 
 	if(dirty_list_.empty()) {
@@ -774,24 +781,46 @@ void twindow::draw()
 		SDL_Rect rect = get_rect();
 		sdl_blit(restorer_, 0, frame_buffer, &rect);
 
-		// Background.
-		for(std::vector<twidget*>::iterator itor = item.begin();
-				itor != item.end(); ++itor) {
+		if(new_widgets) {
+			// Background.
+			for(std::vector<twidget*>::iterator itor = item.begin();
+					itor != item.end(); ++itor) {
 
-			(**itor).draw_background(frame_buffer);
-		}
+				(**itor).draw_background(frame_buffer, 0, 0);
+			}
 
-		// Children.
-		if(!item.empty()) {
-			item.back()->draw_children(frame_buffer);
-		}
+			// Children.
+			if(!item.empty()) {
+				item.back()->draw_children(frame_buffer, 0, 0);
+			}
 
-		// Foreground.
-		for(std::vector<twidget*>::reverse_iterator ritor = item.rbegin();
-				ritor != item.rend(); ++ritor) {
+			// Foreground.
+			for(std::vector<twidget*>::reverse_iterator ritor = item.rbegin();
+					ritor != item.rend(); ++ritor) {
 
-			(**ritor).draw_foreground(frame_buffer);
-			(**ritor).set_dirty(false);
+				(**ritor).draw_foreground(frame_buffer, 0, 0);
+				(**ritor).set_dirty(false);
+			}
+		} else {
+			// Background.
+			for(std::vector<twidget*>::iterator itor = item.begin();
+					itor != item.end(); ++itor) {
+
+				(**itor).draw_background(frame_buffer);
+			}
+
+			// Children.
+			if(!item.empty()) {
+				item.back()->draw_children(frame_buffer);
+			}
+
+			// Foreground.
+			for(std::vector<twidget*>::reverse_iterator ritor = item.rbegin();
+					ritor != item.rend(); ++ritor) {
+
+				(**ritor).draw_foreground(frame_buffer);
+				(**ritor).set_dirty(false);
+			}
 		}
 
 		update_rect(dirty_rect);