Feature: Choose a sensible window size on a fresh OTTD config file. (#8536)

src/openttd.cpp

@@ -708,14 +708,12 @@ int openttd_main(int argc, char *argv[])
 
 	if (resolution.width != 0) _cur_resolution = resolution;
 
-	/*
-	 * The width and height must be at least 1 pixel and width times
-	 * height times bytes per pixel must still fit within a 32 bits
-	 * integer, even for 32 bpp video modes. This way all internal
-	 * drawing routines work correctly.
-	 */
-	_cur_resolution.width  = ClampU(_cur_resolution.width,  1, UINT16_MAX / 2);
-	_cur_resolution.height = ClampU(_cur_resolution.height, 1, UINT16_MAX / 2);
+	/* Limit width times height times bytes per pixel to fit a 32 bit
+	 * integer, This way all internal drawing routines work correctly.
+	 * A resolution that has one component as 0 is treated as a marker to
+	 * auto-detect a good window size. */
+	_cur_resolution.width  = std::min(_cur_resolution.width, UINT16_MAX / 2u);
+	_cur_resolution.height = std::min(_cur_resolution.height, UINT16_MAX / 2u);
 
 	/* Assume the cursor starts within the game as not all video drivers
 	 * get an event that the cursor is within the window when it is opened.

src/table/misc_settings.ini

@@ -120,7 +120,7 @@ name     = ""resolution""
 type     = SLE_INT
 length   = 2
 var      = _cur_resolution
-def      = ""640,480""
+def      = ""0,0""
 cat      = SC_BASIC
 
 [SDTG_STR]

src/video/allegro_v.cpp

@@ -417,6 +417,8 @@ const char *VideoDriver_Allegro::Start(const StringList &parm)
 	}
 	_allegro_instance_count++;
 
+	this->UpdateAutoResolution();
+
 	install_timer();
 	install_mouse();
 	install_keyboard();

src/video/cocoa/cocoa_v.h

@@ -70,6 +70,9 @@ public:
 	/** Main game loop. */
 	void GameLoop(); // In event.mm.
 
+protected:
+	Dimension GetScreenSize() const override;
+
 private:
 	friend class WindowQuartzSubdriver;
 

src/video/cocoa/cocoa_v.mm

@@ -200,6 +200,8 @@ const char *VideoDriver_Cocoa::Start(const StringList &parm)
 	/* Don't create a window or enter fullscreen if we're just going to show a dialog. */
 	if (!CocoaSetupApplication()) return NULL;
 
+	this->UpdateAutoResolution();
+
 	this->orig_res = _cur_resolution;
 	int width  = _cur_resolution.width;
 	int height = _cur_resolution.height;
@@ -302,6 +304,15 @@ void VideoDriver_Cocoa::EditBoxLostFocus()
 	HandleTextInput(NULL, true);
 }
 
+/**
+ * Get the resolution of the main screen.
+ */
+Dimension VideoDriver_Cocoa::GetScreenSize() const
+{
+	NSRect frame = [ [ NSScreen mainScreen ] frame ];
+	return { static_cast<uint>(NSWidth(frame)), static_cast<uint>(NSHeight(frame)) };
+}
+
 /**
  * Handle a change of the display area.
  */

src/video/dedicated_v.cpp

@@ -135,6 +135,8 @@ static FVideoDriver_Dedicated iFVideoDriver_Dedicated;
 
 const char *VideoDriver_Dedicated::Start(const StringList &parm)
 {
+	this->UpdateAutoResolution();
+
 	int bpp = BlitterFactory::GetCurrentBlitter()->GetScreenDepth();
 	_dedicated_video_mem = (bpp == 0) ? nullptr : MallocT<byte>(_cur_resolution.width * _cur_resolution.height * (bpp / 8));
 

src/video/null_v.cpp

@@ -24,6 +24,8 @@ const char *VideoDriver_Null::Start(const StringList &parm)
 	_set_error_mode(_OUT_TO_STDERR);
 #endif
 
+	this->UpdateAutoResolution();
+
 	this->ticks = GetDriverParamInt(parm, "ticks", 1000);
 	_screen.width  = _screen.pitch = _cur_resolution.width;
 	_screen.height = _cur_resolution.height;

src/video/sdl2_v.cpp

@@ -674,6 +674,8 @@ const char *VideoDriver_SDL::Start(const StringList &parm)
 	}
 	if (ret_code < 0) return SDL_GetError();
 
+	this->UpdateAutoResolution();
+
 	GetVideoModes();
 	if (!CreateMainSurface(_cur_resolution.width, _cur_resolution.height, false)) {
 		return SDL_GetError();
@@ -930,4 +932,12 @@ void VideoDriver_SDL::ReleaseBlitterLock()
 	if (_draw_mutex != nullptr) _draw_mutex->unlock();
 }
 
+Dimension VideoDriver_SDL::GetScreenSize() const
+{
+	SDL_DisplayMode mode;
+	if (SDL_GetCurrentDisplayMode(0, &mode) != 0) return VideoDriver::GetScreenSize();
+
+	return { static_cast<uint>(mode.w), static_cast<uint>(mode.h) };
+}
+
 #endif /* WITH_SDL2 */

src/video/sdl2_v.h

@@ -40,6 +40,10 @@ public:
 	void EditBoxLostFocus() override;
 
 	const char *GetName() const override { return "sdl"; }
+
+protected:
+	Dimension GetScreenSize() const override;
+
 private:
 	int PollEvent();
 	void LoopOnce();

src/video/sdl_v.cpp

@@ -614,6 +614,8 @@ const char *VideoDriver_SDL::Start(const StringList &parm)
 	}
 	if (ret_code < 0) return SDL_GetError();
 
+	this->UpdateAutoResolution();
+
 	GetVideoModes();
 	if (!CreateMainSurface(_cur_resolution.width, _cur_resolution.height)) {
 		return SDL_GetError();

src/video/video_driver.hpp

@@ -12,10 +12,19 @@
 
 #include "../driver.h"
 #include "../core/geometry_type.hpp"
+#include "../core/math_func.hpp"
 #include <vector>
 
+extern std::string _ini_videodriver;
+extern std::vector<Dimension> _resolutions;
+extern Dimension _cur_resolution;
+extern bool _rightclick_emulate;
+
 /** The base of all video drivers. */
 class VideoDriver : public Driver {
+	const uint DEFAULT_WINDOW_WIDTH = 640u;  ///< Default window width.
+	const uint DEFAULT_WINDOW_HEIGHT = 480u; ///< Default window height.
+
 public:
 	/**
 	 * Mark a particular area dirty.
@@ -102,11 +111,27 @@ public:
 	static VideoDriver *GetInstance() {
 		return static_cast<VideoDriver*>(*DriverFactoryBase::GetActiveDriver(Driver::DT_VIDEO));
 	}
+
+protected:
+	/*
+	 * Get the resolution of the main screen.
+	 */
+	virtual Dimension GetScreenSize() const { return { DEFAULT_WINDOW_WIDTH, DEFAULT_WINDOW_HEIGHT }; }
+
+	/**
+	 * Apply resolution auto-detection and clamp to sensible defaults.
+	 */
+	void UpdateAutoResolution()
+	{
+		if (_cur_resolution.width == 0 || _cur_resolution.height == 0) {
+			/* Auto-detect a good resolution. We aim for 75% of the screen size.
+			 * Limit width times height times bytes per pixel to fit a 32 bit
+			 * integer, This way all internal drawing routines work correctly. */
+			Dimension res = this->GetScreenSize();
+			_cur_resolution.width  = ClampU(res.width  * 3 / 4, DEFAULT_WINDOW_WIDTH, UINT16_MAX / 2);
+			_cur_resolution.height = ClampU(res.height * 3 / 4, DEFAULT_WINDOW_HEIGHT, UINT16_MAX / 2);
+		}
+	}
 };
 
-extern std::string _ini_videodriver;
-extern std::vector<Dimension> _resolutions;
-extern Dimension _cur_resolution;
-extern bool _rightclick_emulate;
-
 #endif /* VIDEO_VIDEO_DRIVER_HPP */

src/video/win32_v.cpp

@@ -1114,6 +1114,8 @@ static FVideoDriver_Win32 iFVideoDriver_Win32;
 
 const char *VideoDriver_Win32::Start(const StringList &parm)
 {
+	this->UpdateAutoResolution();
+
 	memset(&_wnd, 0, sizeof(_wnd));
 
 	RegisterWndClass();
@@ -1343,3 +1345,8 @@ void VideoDriver_Win32::EditBoxLostFocus()
 	SetCompositionPos(_wnd.main_wnd);
 	SetCandidatePos(_wnd.main_wnd);
 }
+
+Dimension VideoDriver_Win32::GetScreenSize() const
+{
+	return { static_cast<uint>(GetSystemMetrics(SM_CXSCREEN)), static_cast<uint>(GetSystemMetrics(SM_CYSCREEN)) };
+}

src/video/win32_v.h

@@ -40,6 +40,9 @@ public:
 	const char *GetName() const override { return "win32"; }
 
 	bool MakeWindow(bool full_screen);
+
+protected:
+	Dimension GetScreenSize() const override;
 };
 
 /** The factory for Windows' video driver. */