最近几篇教程基本上都是参考着Lazy
Foo的教程顺序来的。因为我也觉得他的顺序很实用。所不同的是，新的类型我都添加在了之前建立起来的surface类的基础之上。所以，如果你觉得单独
看这些教程完全搞不明白，最好从头按照顺序来学习。另外，为了复习C++知识，也为了遵循C++的理念，我有意的将程序风格向C++靠拢。如果你更喜欢C
风格，相信你在其他地方可以找到更适合你的教程。
1.1：一个小细节，SDL窗口的名称
因为涉及到文本的显示了，我们提一个一直以来忽略的问题——SDL建立起来的窗口的名字。因为我们所建立起来的Screen
Surface是唯一和特殊的。所以窗口名字这个行为是可以绑定在这个唯一的Screen Surface对象上的。SDL中的相关函数是：
void SDL_WM_SetCaption(const char *title, const char *icon);
一般icon还暂时用不上，我们设置为空指针。我们修改一下Screen Surface的数据成员与构造函数。在数据成员里面添加一个windowName，并且修改构造函数
class ScreenSurface
{
private:
//
char* windowName;
public:
//
ScreenSurface(int w, int h, char* window_name = 0, int b = 0, Uint32 f = 0);
};
ScreenSurface::ScreenSurface():
width(640), height(480), bpp(32), flags(0), windowName(0)
{
if ( screenNum > 0 )
throw ErrorInfo("DONOT create more than ONE screen!");
if ( SDL_Init(SDL_INIT_VIDEO < 0 ) )
throw ErrorInfo(SDL_GetError());
pScreen = SDL_SetVideoMode(width, height, bpp, flags);
screenNum++;
}
ScreenSurface::ScreenSurface(int w, int h, char* window_name, int b, Uint32 f):
width(w), height(h), bpp(b), flags(f)
{
if ( screenNum > 0 )
throw ErrorInfo("DONOT create more than ONE screen!");
if ( SDL_Init(SDL_INIT_VIDEO < 0 ) )
throw ErrorInfo(SDL_GetError());
pScreen = SDL_SetVideoMode(width, height, bpp, flags);
screenNum++;
if ( window_name != 0 ) {
windowName = window_name;
SDL_WM_SetCaption(windowName, 0);
}
else
windowName = 0;
}
这样，我们在创建SceenSurface的时候，第三个参数如果指定，则可以用字符串表示窗口名称。
1.2：使用*.ttf文件
SDL使用*.ttf文件，仍然需要扩展库的支持。相关的下载和SDL_image的类似，大家可以参考前面的教程。下载地址如下：
使用ttf扩展库的程序如下：
(1)装载扩展库：TTF_Init();
(2)打开字库：TTF_OpenFont(const char* ttf_fileName, int ttf_size);
(3)构建显示文本的surface：TTF_RenderText_Solid(TTF_Font* pFont, const char* message, SDL_Color textColor);
(4)显示（blit）文本surface;
(5)关闭字库：TTF_CloseFont();
(6)退出扩展库：TTF_Quit();
(7)释放显示文本的surface：SDL_FreeSurface();
我们考虑下这个TextSurface与之前的DisplaySurface之间的关系，希望通过类将二者有所联系。
1.3：构建TextSurface类
我们分析下TextSurface与DisplaySurface的关系：他们都依赖于一个ScreenSurface对象，至少具有两个一样的私有数据
成员pSurface和pScreen；他们有一致的行为blit()；他们的构造前提条件不同，析构做的“善后”也不一样。
我在水木社区的CPP版请教有这样关系的两个类应该是什么关系。有前辈指教说，一个类，用不同的flag加以区分。而我并不愿意多增加一个构造函数的参
数，所以，我用构造函数的重载实现构造的不同；用继承类实现方法代码的重用；用继承类的析构函数为TextSurface类做额外的析构工作。
考虑到应在第一次建立TextSurface对象的时候装载ttf扩展库，并在最后一个对象使用完毕后关闭ttf扩展库，所以，在基类
DisplaySurface中添加静态私有成员作为计数器，并添加相应的方法为派生类使用。这些方法，以及专门为派生类创建的基类构造函数，我们并不希
望能被外部使用，所以，使用了关键字proteced。
class DisplaySurface
{
private:
//
//for TextSurafce
static int textNum;
TTF_Font* pFont;
public:
//
protected:
//for TextSurface
DisplaySurface(const std::string& msg_name, const std::string& message, const ScreenSurface& screen,
Uint8 r, Uint8 g, Uint8 b,
const std::string& ttf_fileName, int ttf_size);
int tellTextNum() const;
void reduceTextNum();
void deleteFontPoint();
};
pFont是TextSurface会用到的私有数据，构造基类的时候，直接设置成空指针就可以了。
保护成员的实现如下：
//for TextSurface
DisplaySurface::DisplaySurface(const std::string& msg_name, const std::string& message, const ScreenSurface& screen,
Uint8 r, Uint8 g , Uint8 b,
const std::string& ttf_fileName, int ttf_size):
fileName(msg_name)
{
if ( textNum == 0 )
if ( TTF_Init() < 0 )
throw ErrorInfo("TTF_Init() failed!");
SDL_Color textColor;
textColor.r = r;
textColor.g = g;
textColor.b = b;
pFont = TTF_OpenFont(ttf_fileName.c_str(), ttf_size);
if ( pFont == 0 )
throw ErrorInfo("TTF_OpenFont() failed!");
pSurface = TTF_RenderText_Solid(pFont, message.c_str(), textColor);
if ( pSurface == 0 )
throw ErrorInfo("TTF_RenderText_solid() failed!");
pScreen = screen.point();
textNum++;
}
int DisplaySurface::tellTextNum() const
{
return textNum;
}
void DisplaySurface::reduceTextNum()
{
textNum--;
}
void DisplaySurface::deleteFontPoint()
{
TTF_CloseFont(pFont);
}
有了这些数据成员和方法，我们可以构建TextSurface类了。
class TextSurface: public DisplaySurface
{
public:
TextSurface(const std::string& msg_name, const std::string& message, const ScreenSurface& screen,
Uint8 r = 0xFF, Uint8 g = 0xFF, Uint8 b = 0xFF,
const std::string& ttf_fileName = "lazy.ttf", int ttf_size = 28);
~TextSurface();
};
可以看到，我们仅仅增添了派生类的构造函数和析构函数，实现如下：
//class TextSurface
TextSurface::TextSurface(const std::string& msg_name, const std::string& message, const ScreenSurface& screen,
Uint8 r, Uint8 g, Uint8 b,
const std::string& ttf_fileName, int ttf_size):
DisplaySurface(msg_name, message, screen, r, g, b, ttf_fileName, ttf_size)
{}
TextSurface::~TextSurface()
{
deleteFontPoint();
reduceTextNum();
if ( tellTextNum() == 0 )
TTF_Quit();
}
我们在下节给出完整的代码以及一个用于演示的例子。
//FileName: SurfaceClass.h
#ifndef SURFACE_CLASS_H
#define SURFACE_CLASS_H
#include <iostream>
#include <string>
#include "SDL/SDL.h"
#include "SDL/SDL_image.h"
#include "SDL/SDL_ttf.h"
class ScreenSurface
{
private:
static int screenNum;
int width;
int height;
int bpp;
Uint32 flags;
SDL_Surface* pScreen;
char* windowName;
public:
ScreenSurface();
ScreenSurface(int w, int h, char* window_name = 0, int b = 0, Uint32 f = 0);
~ScreenSurface();
SDL_Surface* point() const;
void flip() const;
void fillColor(Uint8 r = 0, Uint8 g = 0, Uint8 b = 0) const;
};
class DisplaySurface
{
private:
std::string fileName;
SDL_Surface* pSurface;
SDL_Surface* pScreen;
//for TextSurafce
static int textNum;
TTF_Font* pFont;
public:
DisplaySurface(const std::string& file_name, const ScreenSurface& screen);
~DisplaySurface();
SDL_Surface* point() const;
void blit() const;
void blit(int at_x, int at_y) const;
void blit(int at_x, int at_y,
int from_x, int from_y, int w, int h,
int delta_x = 0, int delta_y = 0) const;
void colorKey(Uint8 r = 0, Uint8 g = 0xFF, Uint8 b = 0xFF, Uint32 flag = SDL_SRCCOLORKEY);
protected:
//for TextSurface
DisplaySurface(const std::string& msg_name, const std::string& message, const ScreenSurface& screen,
Uint8 r, Uint8 g, Uint8 b,
const std::string& ttf_fileName, int ttf_size);
int tellTextNum() const;
void reduceTextNum();
void deleteFontPoint();
};
class TextSurface: public DisplaySurface
{
public:
TextSurface(const std::string& msg_name, const std::string& message, const ScreenSurface& screen,
Uint8 r = 0xFF, Uint8 g = 0xFF, Uint8 b = 0xFF,
const std::string& ttf_fileName = "lazy.ttf", int ttf_size = 28);
~TextSurface();
};
class ErrorInfo
{
private:
std::string info;
public:
ErrorInfo():info("Unknown ERROR!")
{}
ErrorInfo(const char* c_str)
{
info = std::string(c_str);
}
ErrorInfo(const std::string& str):info(str)
{}
void show() const
{
std::cerr << info << std::endl;
}
};
#endif
//UVi Soft (2008)
//Long Fei (lf426), E-mail: zbln426@163.com
#include "SurfaceClass.h"
//VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
//class ScreenSurface
int ScreenSurface::screenNum = 0;
ScreenSurface::ScreenSurface():
width(640), height(480), bpp(32), flags(0), windowName(0)
{
if ( screenNum > 0 )
throw ErrorInfo("DONOT create more than ONE screen!");
if ( SDL_Init(SDL_INIT_VIDEO < 0 ) )
throw ErrorInfo(SDL_GetError());
pScreen = SDL_SetVideoMode(width, height, bpp, flags);
screenNum++;
}
ScreenSurface::ScreenSurface(int w, int h, char* window_name, int b, Uint32 f):
width(w), height(h), bpp(b), flags(f)
{
if ( screenNum > 0 )
throw ErrorInfo("DONOT create more than ONE screen!");
if ( SDL_Init(SDL_INIT_VIDEO < 0 ) )
throw ErrorInfo(SDL_GetError());
pScreen = SDL_SetVideoMode(width, height, bpp, flags);
screenNum++;
if ( window_name != 0 ) {
windowName = window_name;
SDL_WM_SetCaption(windowName, 0);
}
else
windowName = 0;
}
ScreenSurface::~ScreenSurface()
{
SDL_Quit();
}
SDL_Surface* ScreenSurface::point() const
{
return pScreen;
}
void ScreenSurface::flip() const
{
if ( SDL_Flip(pScreen) < 0 )
throw ErrorInfo(SDL_GetError());
}
void ScreenSurface::fillColor(Uint8 r, Uint8 g, Uint8 b) const
{
if ( SDL_FillRect(pScreen, 0, SDL_MapRGB(pScreen->format, r, g, b)) < 0 )
throw ErrorInfo(SDL_GetError());
}
//AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
//VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
//class DisplaySurface
int DisplaySurface::textNum = 0;
DisplaySurface::DisplaySurface(const std::string& file_name, const ScreenSurface& screen):
fileName(file_name), pFont(0)
{
SDL_Surface* pSurfaceTemp = IMG_Load(file_name.c_str());
if ( pSurfaceTemp == 0 )
throw ErrorInfo(SDL_GetError());
pSurface = SDL_DisplayFormat(pSurfaceTemp);
if ( pSurface == 0 )
throw ErrorInfo(SDL_GetError());
SDL_FreeSurface(pSurfaceTemp);
pScreen = screen.point();
}
DisplaySurface::~DisplaySurface()
{
SDL_FreeSurface(pSurface);
}
SDL_Surface* DisplaySurface::point() const
{
return pSurface;
}
void DisplaySurface::blit() const
{
if ( SDL_BlitSurface(pSurface, 0, pScreen, 0) < 0 )
throw ErrorInfo(SDL_GetError());
}
void DisplaySurface::blit(int at_x, int at_y) const
{
SDL_Rect offset;
offset.x = at_x;
offset.y = at_y;
if ( SDL_BlitSurface(pSurface, 0, pScreen, &offset) < 0 )
throw ErrorInfo(SDL_GetError());
}
void DisplaySurface::blit(int at_x, int at_y,
int from_x, int from_y, int w, int h,
int delta_x, int delta_y) const
{
SDL_Rect offset;
offset.x = at_x - delta_x;
offset.y = at_y - delta_y;
SDL_Rect dest;
dest.x = from_x - delta_x;
dest.y = from_y - delta_y;
dest.w = w + delta_x*2;
dest.h = h + delta_y*2;
if ( SDL_BlitSurface(pSurface, &dest, pScreen, &offset) < 0 )
throw ErrorInfo(SDL_GetError());
}
void DisplaySurface::colorKey(Uint8 r, Uint8 g, Uint8 b, Uint32 flag)
{
Uint32 colorkey = SDL_MapRGB(pSurface->format, r, g, b);
if ( SDL_SetColorKey(pSurface, flag, colorkey ) < 0 )
throw ErrorInfo(SDL_GetError());
}
//for TextSurface
DisplaySurface::DisplaySurface(const std::string& msg_name, const std::string& message, const ScreenSurface& screen,
Uint8 r, Uint8 g , Uint8 b,
const std::string& ttf_fileName, int ttf_size):
fileName(msg_name)
{
if ( textNum == 0 )
if ( TTF_Init() < 0 )
throw ErrorInfo("TTF_Init() failed!");
SDL_Color textColor;
textColor.r = r;
textColor.g = g;
textColor.b = b;
pFont = TTF_OpenFont(ttf_fileName.c_str(), ttf_size);
if ( pFont == 0 )
throw ErrorInfo("TTF_OpenFont() failed!");
pSurface = TTF_RenderText_Solid(pFont, message.c_str(), textColor);
if ( pSurface == 0 )
throw ErrorInfo("TTF_RenderText_solid() failed!");
pScreen = screen.point();
textNum++;
}
int DisplaySurface::tellTextNum() const
{
return textNum;
}
void DisplaySurface::reduceTextNum()
{
textNum--;
}
void DisplaySurface::deleteFontPoint()
{
TTF_CloseFont(pFont);
}
//AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
//VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
//class TextSurface
TextSurface::TextSurface(const std::string& msg_name, const std::string& message, const ScreenSurface& screen,
Uint8 r, Uint8 g, Uint8 b,
const std::string& ttf_fileName, int ttf_size):
DisplaySurface(msg_name, message, screen, r, g, b, ttf_fileName, ttf_size)
{}
TextSurface::~TextSurface()
{
deleteFontPoint();
reduceTextNum();
if ( tellTextNum() == 0 )
TTF_Quit();
}
//AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
//UVi Soft (2008)
//Long Fei (lf426), E-mail: zbln426@163.com
#include "SurfaceClass.h"
int game(int argc, char* argv[]);
int main(int argc ,char* argv[])
{
int mainRtn = 0;
try {
mainRtn = game(argc, argv);
}
catch ( const ErrorInfo& info ) {
info.show();
return -1;
}
return mainRtn;
}
int game(int argc ,char* argv[])
{
//Create a SDL screen.
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
ScreenSurface screen(SCREEN_WIDTH, SCREEN_HEIGHT, "Font");
//Fill background with white.(default is black)
screen.fillColor(0xFF, 0xFF, 0xFF);
//Load a textSurface
TextSurface myText("logo", "UVi Soft", screen, 0, 0, 0xFF, "times.ttf", 80);
TextSurface lazy("lazy", "by lf426 (zbln426@163.com)", screen, 0xff, 0, 0);
//Display text
myText.blit(170, 180);
lazy.blit(150,400);
screen.flip();
//press ESC or click X to quit.
bool gameOver = false;
SDL_Event gameEvent;
while( gameOver == false ){
while ( SDL_PollEvent(&gameEvent) != 0 ){
if ( gameEvent.type == SDL_QUIT ){
gameOver = true;
}
if ( gameEvent.type == SDL_KEYUP ){
if ( gameEvent.key.keysym.sym == SDLK_ESCAPE ){
gameOver = true;
}
}
}
}
return 0;
}
