SDL Programming Introduction

Initialization 2  The first thing you must do is initialize SDL  int SDL_Init( SDL_INIT_EVERYTHING )  This will return -1 if it fails  Various flags can be OR’ed together to enable various features  In this case, we enable all features

Surfaces 3  A surface is an area where you can draw  The screen is one such surface  You can create other surfaces to hold images or to draw on  You can copy one surface to another  Surfaces have properties  Height  Width  Number of bits per pixel

Creating the Screen 4  After initializing SDL, you create the screen  SDL_Surface *screen;  screen = SDL_SetVideoMode( winWidth, winHeight, screenDepth, SDL_HWSURFACE | SDL_DOUBLEBUF);  The screen depth is usually 32  If the screen cannot be created, NULL will be returned  When a surface is no longer needed it should be freed  SDL_FreeSurface(surface);

Setting a Window Title 5  You can set the title in the top of the window  SDL_WM_SetCaption( “Title", NULL );  The title will be displayed in the window decoration area, usually at the top of the window

SDL Coordinates 6 (0, 0) (100, 0) (0, 100)(100, 100) The origin of a window is the top-left corner Y coordinates increase as we go down The origin of a window is the top-left corner Y coordinates increase as we go down

Loading Images 7  SDL can load images in the BMP format  There are extensions which can load other formats  These extensions must be downloaded and installed into your SDL directories  Loaded images are stored on surfaces  Remember, the screen itself is a surface  You can then copy them from one surface to another to make them appear on the screen

Loading Images 8  To load an image  SDL_Surface *image = SDL_LoadBMP(“file.bmp”);  This will either load the image or return NULL if it cannot be loaded  The trouble is that the image might not have the same format as the screen you want to display it on  You can convert it to the correct format as follows  SDL_Surface *displayImage = SDL_DisplayFormat(image);

Loading Images 9  These steps are done often enough to warrant creating a function or method for loading an image SDL_Surface* loadImage(const char* fileName) { SDL_Surface *tmp = NULL, *image = NULL; tmp = SDL_LoadBMP(fileName); if(tmp) { image = SDL_DisplayFormat(tmp); SDL_FreeSurface(tmp); } return image; }

Rendering Images 10  When you load an image  It is stored on a surface  This does not make the image visible  The image must be copied to the screen to be visible  We move an image using bit blitting  Bit block image transfer  This is done with the function SDL_BlitSurface

SDL_BlitSurface 11  int SDL_BlitSurface( SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect)  Src – source surface  Srcrect – rectangle delimiting areas to copy or NULL for entire image  Dst – the destination surface  Dstrect – position to place on destination surface. If NULL image will be placed at top-left corner  Returns 0 on success

SDL_Rect 12  This is a common structure used to indicate the size and position of rectangular areas typedef struct{ Sint16 x, y; Uint16 w, h; } SDL_Rect;

Event Handling 13  Many events happen while a program is running  Key presses  Mouse movement  Window resizing  Window closing  Games are interested in these events and need to be able to find out when they occur  This can be done using  SDL_PollEvent(& event)

SDL_Event 14 typedef union{ Uint8 type; SDL_ActiveEvent active; SDL_KeyboardEvent key; SDL_MouseMotionEvent motion; SDL_MouseButtonEvent button; SDL_JoyAxisEvent jaxis; SDL_JoyBallEvent jball; SDL_JoyHatEvent jhat; SDL_JoyButtonEvent jbutton; SDL_ResizeEvent resize; SDL_ExposeEvent expose; SDL_QuitEvent quit; SDL_UserEvent user; SDL_SysWMEvent syswm; } SDL_Event; This is used for all event types Note that it is a union The type field indicates which member of the union is to be used This is used for all event types Note that it is a union The type field indicates which member of the union is to be used

SDL Event Types & Structures 15 Event typeEvent Structure SDL_ACTIVEEVENTSDL_ActiveEvent SDL_KEYDOWN/UPSDL_KeyboardEvent SDL_MOUSEMOTIONSDL_MouseMotionEvent SDL_MOUSEBUTTONDOWN/UPSDL_MouseButtonEvent SDL_JOYAXISMOTIONSDL_JoyAxisEvent SDL_JOYBALLMOTIONSDL_JoyBallEvent SDL_JOYHATMOTIONSDL_JoyHatEvent SDL_JOYBUTTONDOWN/UPSDL_JoyButtonEvent SDL_VIDEORESIZESDL_ResizeEvent SDL_VIDEOEXPOSESDL_ExposeEvent SDL_QUITSDL_QuitEvent SDL_USEREVENTSDL_UserEvent SDL_SYSWMEVENTSDL_SysWMEvent

SDL_KeyboardEvent 16 typedef struct{ Uint8 type; Uint8 state; SDL_keysym keysym; } SDL_KeyboardEvent; typedef struct{ Uint8 type; Uint8 state; SDL_keysym keysym; } SDL_KeyboardEvent; FieldValuesDescription typeSDL_KEYDOWN SDL_KEYUP Type of key event StateSDL_KEYPRESSED SDL_KEYRELEASED Same as type keysymStructureThe key pressed

SDL_keysym 17 typedef struct{ Uint8 scancode; SDLKey sym; SDLMod mod; Uint16 unicode; } SDL_keysym; FieldValuesDescription scancodeHardware scan code symSee tableSDL virtual key code modKey modifiers unicodeTranslated character

SDL Key Symbols 18 SDL keyASCIIName SDLK_BACKSPACE'\b'backspace SDLK_TAB'\t'tab SDLK_CLEARclear SDLK_RETURN'\r'return SDLK_PAUSEpause SDLK_ESCAPE'^['escape SDLK_SPACE' space SDLK_EXCLAIM'!'exclamation SDLK_QUOTEDBL'"' double quote SDLK_HASH'#'hash SDLK_DOLLAR'$'dollar SDLK_AMPERSAND'&'ampersand

SDL Key Symbols 19 SDL keyASCIIName SDLK_QUOTE'\''single quote SDLK_LEFTPAREN'('left parenthesis SDLK_RIGHTPARE N ')'right parenthesis SDLK_ASTERISK'*'asterisk SDLK_PLUS'+'plus sign SDLK_COMMA','comma SDLK_MINUS'-'minus sign SDLK_PERIOD'.'period / full stop SDLK_SLASH'/'forward slash SDLK_COLON':'colon SDLK_SEMICOLON';'semicolon SDLK_LESS'<'less-than sign

SDL Key Symbols 20 SDL keyASCI I Name SDLK_EQUALS'='equals sign SDLK_GREATER'>'greater-than sign SDLK_QUESTION'?'question mark SDLK_LEFTBRACKET'['left bracket SDLK_BACKSLASH'\\'backslash SDLK_RIGHTBRACKE T ']'right bracket SDLK_CARET'^'caret SDLK_UNDERSCORE'_'underscore SDLK_DELETE'^?'delete SDLK_UPup arrow SDLK_DOWNdown arrow

SDL Key Symbols 21 SDL keyASCIIName SDLK_RIGHTright arrow SDLK_LEFTleft arrow SDLK_INSERTinsert SDLK_HOMEhome SDLK_ENDend SDLK_PAGEUPpage up SDLK_PAGEDOWNpage down SDLK_F1...F1 SDLK_F15F15 SDLK_PRINTprint-screen SDLK_SYSREQSysRq SDLK_BREAKbreak

SDL Key Symbols 22 SDL keyASCIIName SDLK_0'0'0 SDLK_1'1'1 SDLK_2'2'2 SDLK_3'3'3 SDLK_4'4'4 SDLK_5'5'5 SDLK_6'6'6 SDLK_7'7'7 SDLK_8'8'8 SDLK_9'9'9

SDL Key Symbols 23 SDL keyASCII SDLK_a'a' SDLK_b'b' SDLK_c'c' SDLK_d'd' SDLK_e'e' SDLK_f'f' SDLK_g'g' SDLK_h'h' SDLK_i'i' SDLK_j'j' SDLK_k'k' SDLK_l'l' SDLK_m'm' SDL keyASCII SDLK_n'n' SDLK_o'o' SDLK_p'p' SDLK_q'q' SDLK_r'r' SDLK_s's' SDLK_t't' SDLK_u'u' SDLK_v'v' SDLK_w'w' SDLK_x'x' SDLK_y'y' SDLK_z'z'

Event Processing Loop 24 while(SDL_PollEvent(&event)){ switch(event.type){ case SDL_KEYDOWN: if(event.key.keysym.sym==SDLK_LEFT) move_left(); break;... } } Poll for events and process each of the events

The Game Loop 25 bool quit = false; SDL_Event event; while( quit == false ) { if( SDL_PollEvent( &event ) ) { if( event.type == SDL_QUIT ) { quit = true; } if( SDL_Flip( screen ) == -1 ) { //return 1; } bool quit = false; SDL_Event event; while( quit == false ) { if( SDL_PollEvent( &event ) ) { if( event.type == SDL_QUIT ) { quit = true; } if( SDL_Flip( screen ) == -1 ) { //return 1; } This processes events and keeps the window on the screen until the X in the top right of the window is clicked.

Drawing Text 26  SDL does not support TTF fonts as distributed  You can download the extension from   Get the file  SDL_ttf-devel VC.zip SDL_ttf-devel VC.zip  Open the zip file and  Copy the file in include to the include directory for your SDL  Copy the files in lib to the lib directory for your SDL  You will need to copy the new DLLs to any project that wants to use text

Preparing to Use Text 27  Set the text color SDL_Color textColor; textColor.r = textColor.g = textColor.b = 255;  Initialize the TTF extension if( TTF_Init() == -1 ) { return false; }  Load the font if( NULL == (font = TTF_OpenFont( "lazy.ttf", 28 )) ) { return false; }

Rendering the Text 28  text is rendered to a newly created surface  You then copy this surface onto the surface where the text should appear textSurface = TTF_RenderText_Solid( font, "A-Maze-ing", textColor );  This surface is then blitted onto the destination surface

Colors 29  Colors are specified as  RGB with each value from 0 – 255  There are two different structures  An unsigned 32 bit int  An SDL_Color structure  SDL_Color has members  r, g, b  To create the 32 bit int unsigned int color = SD_MapRGB(screen->format, 255, 255, 255);

Drawing Lines & Rectangles 30 int SDL_DrawLine(SDL_Surface* dst, int x1, int y1, int x2, int y2, Uint32 color) int SDL_FillRect(SDL_Surface *dst, SDL_Rect *dstrect, Uint32 color)  Both functions return 0 on success