Mint_21.3 drawing-area和goocanvas的FB笔记(五)

FreeBASIC SDL图形功能

SDL - Simple DirectMedia Layer 是完整的跨平台系统，有自己的窗口、直接捕获键盘、鼠标和游戏操纵杆的事件，直接操作音频和CDROM，在其surface上可使用gfx, openGL和direct3D绘图。Window3.0时代，各种应用程序在Pharlap、DJPP、4GW支持下均突破了常规内存进入了保护模式，因此那个时期是SDL突破性发展的时机，非常多的游戏程序用SDL做支撑(gtk/iup/libui有的功能sdl没有，而sdl有的能力其它的则没有)，是开发游戏和工厂流程化应用绘图的优秀工具。C#, Lua, Rust, hollywood, beaflang, Ocamel, Python, 等众多语言有它的封装， Github上的最新稳定版是 2.30.1 ，三天前还在更新。

Github上各平台使用的SDL

游戏：wildfire 野火

DOSBOX: DOS simulator

Humble Bundle 各种游戏

valve 众多游戏

FreeBASIC 完美支持 SDL, 需要安装如下 .so 库文件(SDL, SDL2 二个版本)

#freebasic SDL
sudo apt install libsdl2-dev
sudo apt install libsdl2-ttf-dev
sudo apt install libsdl2-net-dev
sudo apt install libsdl2-mixer-dev
sudo apt install libsdl2-image-dev
sudo apt install libsdl2-gfx-dev
sudo apt install libsdl1.2-dev
sudo apt install libsdl-console-dev
sudo apt install libsdl-mixer1.2-dev
sudo apt install libsdl-gfx1.2-dev
sudo apt install libsdl-net1.2-dev
sudo apt install libsdl-pango-dev
sudo apt install libsdl-sge-dev
sudo apt install libsdl-sound1.2-dev

示例一：放三个图文件：free.jpg, basic.gif, horse.tga

SDL库可读取的的图形文件种类繁多，此示例是在原示例基础上修改的，读取 gif, tga, jpg三种格式的文件。程序首选获取SDL的版本号，初始化 sdl, 作为三个sdl surface装入图形文件并返回图形指针，然后在不同位置放置它们，最后flip显示它们。

' SDL_image example written by Edmond Leung (leung.edmond@gmail.com)
'
' free.jpg, basic.gif and horse.tga are taken from the official freeBasic
' website.

#include  "SDL\SDL.bi"
#include  "SDL\SDL_image.bi"

declare sub blitImage _
   (byval img as SDL_Surface ptr, byval x as integer, byval y as integer)

	dim shared video as SDL_Surface ptr

	dim freeImg as SDL_Surface ptr, basicImg as SDL_Surface ptr, horseImg as SDL_Surface ptr

	dim version as const SDL_version ptr
	version = IMG_Linked_Version()

	' display the version number of the SDL_image being used
	print "Using SDL_image version number: "; SDL_VERSIONNUM(version->major, _
   	version->minor, version->patch)

	' initialise sdl with video support
	if (SDL_Init(SDL_INIT_VIDEO) < 0) then
   		print "Couldn't initialise SDL: "; *SDL_GetError()
	end if

	' check to see if the images are in the correct formats
	if (IMG_isJPG(SDL_RWFromFile("data/free.jpg", "rb")) = 0) then
   		print "The image (free.jpg) is not a jpg file."
	end if
	if (IMG_isGIF(SDL_RWFromFile("data/basic.gif", "rb")) = 0) then
   		print "The image (basic.gif) is not a gif file."
	end if

	' set the video mode to 1024x768x32bpp
	video = SDL_SetVideoMode(1024, 768, 32, SDL_HWSURFACE or SDL_DOUBLEBUF)
	
	if (video = NULL) then
   		print "Couldn't set video mode: "; *SDL_GetError()
	end if

	' load the images into an SDL_RWops structure
	dim freeRw as SDL_RWops ptr, basicRw as SDL_RWops ptr
	freeRw = SDL_RWFromFile("data/free.jpg", "rb")
	basicRw = SDL_RWFromFile("data/basic.gif", "rb")

	' load the images onto an SDL_Surface using three different functions available
	' in the SDL_image library
	freeImg = IMG_LoadJPG_RW(freeRw)
	horseImg = IMG_Load("data/horse.tga")
	basicImg = IMG_LoadTyped_RW(basicRw, 1, "gif")

	dim done as integer
	done = 0

	do while (done = 0)
   		dim event as SDL_Event
   
   		do while (SDL_PollEvent(@event))
      		if (event.type = SDL_QUIT_) then done = 1
      			if (event.type = SDL_KEYDOWN) then
        	 		if (event.key.keysym.sym = SDLK_ESCAPE) then done = 1      
      		end if
   		loop

   		dim destrect as SDL_Rect
   		destrect.w = video->w
   		destrect.h = video->h
   
   		' clear the screen with the colour white
   		SDL_FillRect(video, @destrect, SDL_MapRGB(video->format, 255, 255, 255))
   
   		' draw the images onto the screen

		blitImage freeImg, 170, 205

   		blitImage horseImg, 345, 330 
		blitImage freeImg, 445, 335 
   		blitImage basicImg, 450, 360 
		
		blitImage freeImg, 650, 215 
   		blitImage basicImg, 650, 240 		

		blitImage freeImg, 150, 455 
   		blitImage basicImg, 150, 480 		
	
		SDL_Flip(video)
	loop

	SDL_Quit

' sub-routine used to help with blitting the images onto the screen
sub blitImage _
   (byval img as SDL_Surface ptr, byval x as integer, byval y as integer)
	dim dest as SDL_Rect
   	dest.x = x
   	dest.y = y
   	SDL_BlitSurface(img, NULL, video, @dest)
end sub

示例二：对网络的支持，访问百度站点并取得首页面前部分内容(对于现代编程，这好像是非常基本的能力)。

''
'' simple http get example using the SDL_net library
''

#include once "SDL/SDL_net.bi"

const RECVBUFFLEN = 8192
const NEWLINE = !"\r\n"
'const DEFAULT_HOST = "www.freebasic.net"
const DEFAULT_HOST = "www.baidu.com"

declare sub gethostandpath( byref src as string, byref hostname as string, byref path as string )
	
	
	'' globals
	dim hostname as string
	dim path as string
	
	gethostandpath command, hostname, path
	
	if( len( hostname ) = 0 ) then
		hostname = DEFAULT_HOST
	end if
	
	'' init
	if( SDLNet_Init <> 0 ) then
		print "Error: SDLNet_Init failed"
		end 1
	end if
                         
	'' resolve
	dim ip as IPAddress
    dim socket as TCPSocket
    
    if( SDLNet_ResolveHost( @ip, hostname, 80 ) <> 0 ) then
		print "Error: SDLNet_ResolveHost failed"
		end 1
	end if
    
    '' open
    socket = SDLNet_TCP_Open( @ip )
    if( socket = 0 ) then
		print "Error: SDLNet_TCP_Open failed"
		end 1
	end if
    
    '' send HTTP request
    dim sendbuffer as string
    
	sendBuffer = "GET /" + path + " HTTP/1.0" + NEWLINE + _
				 "Host: " + hostname + NEWLINE + _
				 "Connection: close" + NEWLINE + _
				 "User-Agent: GetHTTP 0.0" + NEWLINE + _
				 NEWLINE
				 
    if( SDLNet_TCP_Send( socket, strptr( sendbuffer ), len( sendbuffer ) ) < len( sendbuffer ) ) then
		print "Error: SDLNet_TCP_Send failed"
		end 1
	end if
    
    '' receive til connection is closed
    dim recvbuffer as zstring * RECVBUFFLEN+1
    dim bytes as integer
    
    do 
    	bytes = SDLNet_TCP_Recv( socket, strptr( recvbuffer ), RECVBUFFLEN )
    	if( bytes <= 0 ) then
    		exit do
    	end if
    	
    	'' add the null-terminator
    	recvbuffer[bytes] = 0
    	
    	'' print it as string
    	print recvbuffer;
    loop
    print
                         
	'' close socket
	SDLNet_TCP_Close( socket )
	
	'' quit
	SDLNet_Quit

'':::::
sub gethostandpath( byref src as string, byref hostname as string, byref path as string )
	dim p as integer
	
	p = instr( src, " " )
	if( p = 0 or p = len( src ) ) then
		hostname = trim( src )
		path = ""
	else
		hostname = trim( left( src, p-1 ) )
		path = trim( mid( src, p+1 ) )
	end if
		
end sub

示例三：SDL 对 gfx 的支持。画任意线条，非常经典的dos年代的一款demo

''
'' simple http get example using the SDL_net library
''

#include once "SDL/SDL_net.bi"

const RECVBUFFLEN = 8192
const NEWLINE = !"\r\n"
'const DEFAULT_HOST = "www.freebasic.net"
const DEFAULT_HOST = "www.baidu.com"

declare sub gethostandpath( byref src as string, byref hostname as string, byref path as string )
	
	
	'' globals
	dim hostname as string
	dim path as string
	
	gethostandpath command, hostname, path
	
	if( len( hostname ) = 0 ) then
		hostname = DEFAULT_HOST
	end if
	
	'' init
	if( SDLNet_Init <> 0 ) then
		print "Error: SDLNet_Init failed"
		end 1
	end if
                         
	'' resolve
	dim ip as IPAddress
    dim socket as TCPSocket
    
    if( SDLNet_ResolveHost( @ip, hostname, 80 ) <> 0 ) then
		print "Error: SDLNet_ResolveHost failed"
		end 1
	end if
    
    '' open
    socket = SDLNet_TCP_Open( @ip )
    if( socket = 0 ) then
		print "Error: SDLNet_TCP_Open failed"
		end 1
	end if
    
    '' send HTTP request
    dim sendbuffer as string
    
	sendBuffer = "GET /" + path + " HTTP/1.0" + NEWLINE + _
				 "Host: " + hostname + NEWLINE + _
				 "Connection: close" + NEWLINE + _
				 "User-Agent: GetHTTP 0.0" + NEWLINE + _
				 NEWLINE
				 
    if( SDLNet_TCP_Send( socket, strptr( sendbuffer ), len( sendbuffer ) ) < len( sendbuffer ) ) then
		print "Error: SDLNet_TCP_Send failed"
		end 1
	end if
    
    '' receive til connection is closed
    dim recvbuffer as zstring * RECVBUFFLEN+1
    dim bytes as integer
    
    do 
    	bytes = SDLNet_TCP_Recv( socket, strptr( recvbuffer ), RECVBUFFLEN )
    	if( bytes <= 0 ) then
    		exit do
    	end if
    	
    	'' add the null-terminator
    	recvbuffer[bytes] = 0
    	
    	'' print it as string
    	print recvbuffer;
    loop
    print
                         
	'' close socket
	SDLNet_TCP_Close( socket )
	
	'' quit
	SDLNet_Quit

'':::::
sub gethostandpath( byref src as string, byref hostname as string, byref path as string )
	dim p as integer
	
	p = instr( src, " " )
	if( p = 0 or p = len( src ) ) then
		hostname = trim( src )
		path = ""
	else
		hostname = trim( left( src, p-1 ) )
		path = trim( mid( src, p+1 ) )
	end if
		
end sub

示例四：SDL 对open_GL的支持。简单的三角形，颜色glColor3f 后面带3个float参数; glVertext3f, 顶点描述后面带3个float参数。

''
'' gltest.bas - freeBASIC opengl example, using GLUT for simplicity
'' by Blitz
''
'' Opengl code ported from nehe's gl tutorials
''

#include once "GL/gl.bi"
#include once "GL/glu.bi"
#include once "GL/glut.bi"

''
declare sub         doMain           ( )
declare sub         doShutdown		 ( )



    ''
    '' Entry point
    ''
    doMain
    

    

'' ::::::::::::
'' name: doRender
'' desc: Is called by glut to render scene
''
'' ::::::::::::
sub doRender cdecl
    static rtri as single
    static rqud as single
    
    glClear GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT
    glPushMatrix
    
    glLoadIdentity
    glTranslatef -1.5, 0.0, -6.0
    glRotatef rtri, 0, 1, 0
         
    glBegin GL_TRIANGLES
		glColor3f   1.0, 0.0, 0.0			'' Red
		glVertex3f  0.0, 1.0, 0.0			'' Top Of Triangle  Front)
		glColor3f   0.0, 1.0, 0.0			'' Green
		glVertex3f -1.0,-1.0, 1.0			'' Left Of Triangle  Front)
		glColor3f   0.0, 0.0, 1.0			'' Blue
		glVertex3f  1.0,-1.0, 1.0			'' Right Of Triangle  Front)
		glColor3f   1.0, 0.0, 0.0			'' Red
		glVertex3f  0.0, 1.0, 0.0			'' Top Of Triangle  Right)
		glColor3f   0.0, 0.0, 1.0			'' Blue
		glVertex3f  1.0,-1.0, 1.0			'' Left Of Triangle  Right)
		glColor3f   0.0, 1.0, 0.0			'' Green
		glVertex3f  1.0,-1.0,-1.0			'' Right Of Triangle  Right)
        glColor3f   1.0, 0.0, 0.0			'' Red
		glVertex3f  0.0, 1.0, 0.0			'' Top Of Triangle  Back)
		glColor3f   0.0, 1.0, 0.0			'' Green
		glVertex3f  1.0,-1.0,-1.0			'' Left Of Triangle  Back)
		glColor3f   0.0, 0.0, 1.0			'' Blue
		glVertex3f -1.0,-1.0,-1.0			'' Right Of Triangle  Back)
		glColor3f   1.0, 0.0, 0.0			'' Red
		glVertex3f  0.0, 1.0, 0.0			'' Top Of Triangle  Left)
		glColor3f   0.0, 0.0, 1.0			'' Blue
		glVertex3f -1.0,-1.0,-1.0			'' Left Of Triangle  Left)
		glColor3f   0.0, 1.0, 0.0			'' Green
		glVertex3f -1.0,-1.0, 1.0			'' Right Of Triangle  Left)
    glEnd
    
    glColor3f 0.5, 0.5, 1.0
    glLoadIdentity    
    glTranslatef -1.5, 0.0, -6.0
	glTranslatef 3.0,0.0,0.0	
	glRotatef rqud, 1.0, 0.0, 0.0
	
	glBegin GL_QUADS
		glVertex3f -1.0, 1.0, 0.0
		glVertex3f  1.0, 1.0, 0.0
		glVertex3f  1.0,-1.0, 0.0
		glVertex3f -1.0,-1.0, 0.0
	glEnd    

    glPopMatrix            
    glutSwapBuffers
    
    rtri = rtri + 2.0
    rqud = rqud + 1.5
    
end sub



'' ::::::::::::
'' name: doInput
'' desc: Handles input
''
'' ::::::::::::
sub doInput CDECL ( byval kbcode as unsigned byte, _
              byval mousex as integer, _
              byval mousey as integer )
              
    if ( kbcode = 27 ) then
        doShutdown
        end 0
    end if

end sub



'' ::::::::::::
'' name: doInitGL
'' desc: Inits OpenGL
''
'' ::::::::::::
sub doInitGL
    dim i as integer
    dim lightAmb(3) as single
    dim lightDif(3) as single
    dim lightPos(3) as single
    
    ''
    '' Rendering stuff
    ''
    glShadeModel GL_SMOOTH
	glClearColor 0.0, 0.0, 0.0, 0.5
	glClearDepth 1.0
	glEnable GL_DEPTH_TEST
	glDepthFunc GL_LEQUAL
    glEnable GL_COLOR_MATERIAL
	glHint GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST
    
    ''
    '' Light setup ( not used at the moment )
    ''
    for i = 0 to 3
        lightAmb(i) = 0.5
        lightDif(i) = 1.0
        lightPos(i) = 0.0
    next i

    lightAmb(3) = 1.0
    lightPos(2) = 2.0
    lightPos(3) = 1.0    
	
    glLightfv GL_LIGHT1, GL_AMBIENT, @lightAmb(0)
	glLightfv GL_LIGHT1, GL_DIFFUSE, @lightDif(0)
	glLightfv GL_LIGHT1, GL_POSITION,@lightPos(0)
	glEnable GL_LIGHT1

    ''
    '' Blending ( not used at the moment )
    ''
    glColor4f 1.0, 1.0, 1.0, 0.5
    glBlendFunc GL_SRC_ALPHA, GL_ONE

end sub



'' ::::::::::::
'' name: doReshapeGL
'' desc: Reshapes GL window
''
'' ::::::::::::
sub doReshapeGL CDECL ( byval w as integer, _
                        byval h as integer )
    
    glViewport 0, 0, w, h 
    glMatrixMode GL_PROJECTION
    glLoadIdentity
    
    if ( h = 0 ) then
        gluPerspective  80/2, w, 1.0, 5000.0 
    else
        gluPerspective  80/2, w / h, 1.0, 5000.0
    end if
    
    glMatrixMode GL_MODELVIEW
    glLoadIdentity

end sub

'':::::
sub initGLUT
    ''
    '' Setup glut
    ''
    glutInit 1, strptr( " " )    
    
    glutInitWindowPosition 0, 0
    glutInitWindowSize 640, 480
    glutInitDisplayMode GLUT_RGBA or GLUT_DOUBLE or GLUT_DEPTH
    glutCreateWindow "FreeBASIC OpenGL example"
    
    doInitGL
    
    glutDisplayFunc  @doRender
    glutIdleFunc     @doRender
    glutReshapeFunc  CAST(Any PTR, @doReshapeGL)
    glutKeyboardFunc CAST(Any PTR, @doInput)

end sub

'':::::
sub doInit
    
	''
	'' Init GLUT
	''
	initGLUT    
	
end sub

'':::::
sub shutdownGLUT

	'' GLUT shutdown will be done automatically by atexit()

end sub

'':::::
sub doShutdown
    
	''
	'' GLUT
	''
	shutdownGLUT
	
end sub

'' ::::::::::::
'' name: doMain
'' desc: Main routine
''
'' ::::::::::::
sub doMain
    
    ''
    '' 
    ''
    doInit
    
    ''
    ''
    ''
    glutMainLoop
    
end sub

SDL 对鼠标、键盘、joysticker的响应都比较好。以前研究鼠标鉴相时拆过几个滚球鼠标，通过串口可以读取字节形式的位置信息，游戏操纵杆还没拆过，有时间了拆解一个研究一下它的button和位置实现，估计和早期原理图有很多不同。SDL内容太多，先熟悉它的功能和应用领域，没有做更深入的学习，以后用的话还要多补补课。