Implement taking smallmap screenshots.

This is largely based on this patch:
http://www.tt-forums.net/viewtopic.php?p=849533#p849533
with the following changes:
* this uses a button in the smallmap window instead of a console command
* screenshot now uses zoom level and mode of smallmap window

src/lang/english.txt

@@ -753,6 +753,7 @@ STR_SMALLMAP_INDUSTRY                                           :{TINY_FONT}{STR
 STR_SMALLMAP_LINKSTATS                                          :{TINY_FONT}{STRING}
 STR_SMALLMAP_COMPANY                                            :{TINY_FONT}{COMPANY}
 STR_SMALLMAP_TOWN                                               :{TINY_FONT}{WHITE}{TOWN}
+STR_SMALLMAP_SCREENSHOT                                         :{BLACK}Screenshot
 STR_SMALLMAP_DISABLE_ALL                                        :{BLACK}Disable all
 STR_SMALLMAP_ENABLE_ALL                                         :{BLACK}Enable all
 STR_SMALLMAP_SHOW_HEIGHT                                        :{BLACK}Show height

src/screenshot.cpp

@@ -25,6 +25,7 @@
 #include "window_func.h"
 #include "tile_map.h"
 #include "landscape.h"
+#include "smallmap_gui.h"
 
 #include "table/strings.h"
 
@@ -810,6 +811,20 @@ bool MakeHeightmapScreenshot(const char *filename)
 	return sf->proc(filename, HeightmapCallback, NULL, MapSizeX(), MapSizeY(), 8, palette);
 }
 
+/**
+ * Show a a success or failure message indicating the result of a screenshot action
+ * @param ret  whether the screenshot action was successful
+ */
+static void ShowScreenshotResultMessage(bool ret)
+{
+	if (ret) {
+		SetDParamStr(0, _screenshot_name);
+		ShowErrorMessage(STR_MESSAGE_SCREENSHOT_SUCCESSFULLY, INVALID_STRING_ID, WL_WARNING);
+	} else {
+		ShowErrorMessage(STR_ERROR_SCREENSHOT_FAILED, INVALID_STRING_ID, WL_ERROR);
+	}
+}
+
 /**
  * Make an actual screenshot.
  * @param t    the type of screenshot to make.
@@ -856,12 +871,37 @@ bool MakeScreenshot(ScreenshotType t, const char *name)
 			NOT_REACHED();
 	}
 
-	if (ret) {
-		SetDParamStr(0, _screenshot_name);
-		ShowErrorMessage(STR_MESSAGE_SCREENSHOT_SUCCESSFULLY, INVALID_STRING_ID, WL_WARNING);
-	} else {
-		ShowErrorMessage(STR_ERROR_SCREENSHOT_FAILED, INVALID_STRING_ID, WL_ERROR);
-	}
+	ShowScreenshotResultMessage(ret);
 
 	return ret;
 }
+
+/**
+ * Callback for generating a smallmap screenshot.
+ * @param userdata SmallMapWindow window pointer
+ * @param buf Videobuffer with same bitdepth as current blitter
+ * @param y First line to render
+ * @param pitch Pitch of the videobuffer
+ * @param n Number of lines to render
+ */
+static void SmallMapCallback(void *userdata, void *buf, uint y, uint pitch, uint n)
+{
+	SmallMapWindow *window = static_cast<SmallMapWindow *>(userdata);
+	window->ScreenshotCallbackHandler(buf, y, pitch, n);
+}
+
+/**
+ * Make a screenshot of the smallmap
+ * @param width   the width of the screenshot
+ * @param height  the height of the screenshot
+ * @param window  a pointer to the smallmap window to use, the current mode and zoom status of the window is used for the screenshot
+ * @return true iff the screenshot was made successfully
+ */
+bool MakeSmallMapScreenshot(unsigned int width, unsigned int height, SmallMapWindow *window)
+{
+	_screenshot_name[0] = '\0';
+	const ScreenshotFormat *sf = _screenshot_formats + _cur_screenshot_format;
+	bool ret = sf->proc(MakeScreenshotName(SCREENSHOT_NAME, sf->extension), SmallMapCallback, window, width, height, BlitterFactory::GetCurrentBlitter()->GetScreenDepth(), _cur_palette.palette);
+	ShowScreenshotResultMessage(ret);
+	return ret;
+}

src/screenshot.h

@@ -26,8 +26,11 @@ enum ScreenshotType {
 	SC_HEIGHTMAP,   ///< Heightmap of the world.
 };
 
+class SmallMapWindow;
+
 void SetupScreenshotViewport(ScreenshotType t, struct ViewPort *vp);
 bool MakeHeightmapScreenshot(const char *filename);
+bool MakeSmallMapScreenshot(unsigned int width, unsigned int height, SmallMapWindow *window);
 bool MakeScreenshot(ScreenshotType t, const char *name);
 
 extern char _screenshot_format_name[8];

src/smallmap_gui.cpp

@@ -23,6 +23,7 @@
 #include "sound_func.h"
 #include "window_func.h"
 #include "company_base.h"
+#include "screenshot.h"
 
 #include "smallmap_gui.h"
 
@@ -936,7 +937,7 @@ void SmallMapWindow::DrawMapIndicators() const
  *
  * @param dpi pointer to pixel to write onto
  */
-void SmallMapWindow::DrawSmallMap(DrawPixelInfo *dpi) const
+void SmallMapWindow::DrawSmallMap(DrawPixelInfo *dpi, bool draw_indicators) const
 {
 	Blitter *blitter = BlitterFactory::GetCurrentBlitter();
 	DrawPixelInfo *old_dpi;
@@ -992,7 +993,7 @@ void SmallMapWindow::DrawSmallMap(DrawPixelInfo *dpi) const
 	if (this->show_towns) this->DrawTowns(dpi);
 
 	/* Draw map indicators */
-	this->DrawMapIndicators();
+	if (draw_indicators) this->DrawMapIndicators();
 
 	_cur_dpi = old_dpi;
 }
@@ -1487,6 +1488,10 @@ int SmallMapWindow::GetPositionOnLegend(Point pt)
 			this->SetWidgetLoweredState(WID_SM_SHOW_HEIGHT, _smallmap_show_heightmap);
 			this->SetDirty();
 			break;
+
+		case WID_SM_SCREENSHOT:
+			TakeScreenshot();
+			break;
 	}
 }
 
@@ -1650,6 +1655,71 @@ Point SmallMapWindow::GetStationMiddle(const Station *st) const
 	return ret;
 }
 
+/**
+ * Take a screenshot of the contents of the smallmap window, at the current zoom level and mode
+ * This calls MakeSmallMapScreenshot which uses ScreenshotCallbackHandler as the screenshot callback
+ */
+void SmallMapWindow::TakeScreenshot()
+{
+	int32 width = ((MapMaxX() + MapMaxY()) * 2) / this->zoom;
+	int32 height = (MapMaxX() + MapMaxY() + 1) / this->zoom;
+
+	int32 saved_scroll_x = this->scroll_x;
+	int32 saved_scroll_y = this->scroll_y;
+	int32 saved_subscroll = this->subscroll;
+	this->subscroll = 0;
+	MakeSmallMapScreenshot(width, height, this);
+	this->scroll_x = saved_scroll_x;
+	this->scroll_y = saved_scroll_y;
+	this->subscroll = saved_subscroll;
+}
+
+/**
+ * Callback called by the screenshot code to draw a section of the smallmap to the output buffer
+ * @param buf Videobuffer with same bitdepth as current blitter
+ * @param y First line to render
+ * @param pitch Pitch of the videobuffer
+ * @param n Number of lines to render
+ */
+void SmallMapWindow::ScreenshotCallbackHandler(void *buf, uint y, uint pitch, uint n)
+{
+	DrawPixelInfo dpi, *old_dpi;
+
+	/* We are no longer rendering to the screen */
+	DrawPixelInfo old_screen = _screen;
+	bool old_disable_anim = _screen_disable_anim;
+
+	_screen.dst_ptr = buf;
+	_screen.width = pitch;
+	_screen.height = n;
+	_screen.pitch = pitch;
+	_screen_disable_anim = true;
+
+	old_dpi = _cur_dpi;
+	_cur_dpi = &dpi;
+
+	dpi.dst_ptr = buf;
+	dpi.height = n;
+	dpi.width = ((MapMaxX() + MapMaxY()) * 2) / this->zoom;
+	dpi.pitch = pitch;
+	dpi.zoom = ZOOM_LVL_NORMAL;
+	dpi.left = 0;
+	dpi.top = y;
+
+	int32 pos = (((int32)MapMaxX() + 1) * TILE_PIXELS) / 4;
+	this->scroll_x = pos;
+	this->scroll_y = -pos;
+
+	/* make the screenshot */
+	this->DrawSmallMap(&dpi, false);
+
+	_cur_dpi = old_dpi;
+
+	/* Switch back to rendering to the screen */
+	_screen = old_screen;
+	_screen_disable_anim = old_disable_anim;
+}
+
 SmallMapWindow::SmallMapType SmallMapWindow::map_type = SMT_CONTOUR;
 bool SmallMapWindow::show_towns = true;
 int SmallMapWindow::max_heightlevel = -1;
@@ -1798,6 +1868,7 @@ static const NWidgetPart _nested_smallmap_widgets[] = {
 	NWidgetFunction(SmallMapDisplay), // Smallmap display and legend bar + image buttons.
 	/* Bottom button row and resize box. */
 	NWidget(NWID_HORIZONTAL),
+		NWidget(WWT_PUSHTXTBTN, COLOUR_BROWN, WID_SM_SCREENSHOT), SetDataTip(STR_SMALLMAP_SCREENSHOT, STR_NULL),
 		NWidget(NWID_SELECTION, INVALID_COLOUR, WID_SM_SELECT_BUTTONS),
 			NWidget(NWID_HORIZONTAL, NC_EQUALSIZE),
 				NWidget(WWT_PUSHTXTBTN, COLOUR_BROWN, WID_SM_ENABLE_ALL), SetDataTip(STR_SMALLMAP_ENABLE_ALL, STR_NULL),

src/smallmap_gui.h

@@ -157,7 +157,7 @@ protected:
 	void DrawSmallMapColumn(void *dst, uint xc, uint yc, int pitch, int reps, int start_pos, int end_pos, Blitter *blitter) const;
 	void DrawVehicles(const DrawPixelInfo *dpi, Blitter *blitter) const;
 	void DrawTowns(const DrawPixelInfo *dpi) const;
-	void DrawSmallMap(DrawPixelInfo *dpi) const;
+	void DrawSmallMap(DrawPixelInfo *dpi, bool draw_indicators = true) const;
 
 	Point RemapTile(int tile_x, int tile_y) const;
 	Point PixelToTile(int px, int py, int *sub, bool add_sub = true) const;
@@ -189,6 +189,9 @@ public:
 	virtual void OnTick();
 	virtual void OnScroll(Point delta);
 	virtual void OnMouseOver(Point pt, int widget);
+
+	void TakeScreenshot();
+	void ScreenshotCallbackHandler(void *buf, uint y, uint pitch, uint n);
 };
 
 #endif /* SMALLMAP_GUI_H */

src/widgets/smallmap_widget.h

@@ -34,6 +34,7 @@ enum SmallMapWidgets {
 	WID_SM_ENABLE_ALL,     ///< Button to enable display of all legend entries.
 	WID_SM_DISABLE_ALL,    ///< Button to disable display of all legend entries.
 	WID_SM_SHOW_HEIGHT,    ///< Show heightmap toggle button.
+	WID_SM_SCREENSHOT,     ///< Button to take smallmap screenshots
 };
 
 #endif /* WIDGETS_SMALLMAP_WIDGET_H */