我正在开发一个跨平台游戏引擎,它运行得很好(我使用的是SDL)。然而,我想要一种简单的方式来向用户显示消息框,而不必依赖SDL或OpenGL(渲染到屏幕上),例如,如果窗口已损坏或尚未创建,因此我无法将消息渲染到屏幕,该怎么办?
我已经实现了一个消息框函数,每个平台有多个实现:Windows实现使用MessageBox,Mac OS X实现使用Cocoa的NSAlert,我不知道linux实现可以使用什么。我想到X11是因为SDL在linux上使用X11进行窗口化。
我尝试过其他答案,但它们要么太模糊,要么要求我用X11或其他东西重新装配整个游戏引擎。我正在努力寻找一个独立于应用程序的解决方案(比如可以在控制台应用程序中使用的windows MessageBox函数)。
注意:Mac和Windows实现的所有代码都很好——这只是我需要帮助的Linux实现。
哦,当我在Mac OS X上编译时,我利用了Objective-C++,这样我就可以将Cocoa(Objective-C)与我的C++msgbox()函数混合使用。
这是我迄今为止为Windows&Mac实现:
消息框.h
#ifndef MSGBOX_H
#define MSGBOX_H
//Cross-platform message box method.
#include "platform.h"
#include "string.h"
//This is my own cross platform enum for message boxes.
//This enumeration 'overlaps' with some declarations in windows.h but that is fine.
enum //Message box values.
{
MB_OK, //For OK message box and return value.
MB_OKCANCEL,
MB_YESNO,
MB_RETRYCANCEL,
MB_YESNOCANCEL,
MB_ABORTRETRYIGNORE,
MB_CANCELTRYCONTINUE,
MB_CANCEL,
MB_YES,
MB_NO,
MB_RETRY,
MB_IGNORE,
MB_TRYAGAIN,
MB_CONTINUE,
MB_ABORT,
};
//The message box function (multiple implementations for each platform).
int msgbox(string msg, string title, int buttons);
#endif // MSGBOX_H
msgbox.cpp
#include "msgbox.h"
#if CURRENT_PLATFORM == PLATFORM_WINDOWS //We can use the windows API for our messagebox.
#include <windows.h> //For the message box function.
#define IDTRYAGAIN 10 //Some fixes to help this application compile.
#define IDCONTINUE 11
int msgbox(string msg, string title, int buttons)
{
//Display the mesagebox.
int retval = MessageBox(NULL, msg.c_str(), title.c_str(), buttons | MB_ICONEXCLAMATION | MB_SYSTEMMODAL);
//Map the windows return value to ours.
switch(retval)
{
case IDOK: return MB_OK;
case IDCANCEL: return MB_CANCEL;
case IDYES: return MB_YES;
case IDNO: return MB_NO;
case IDRETRY: return MB_RETRY;
case IDIGNORE: return MB_IGNORE;
case IDTRYAGAIN:return MB_TRYAGAIN;
case IDCONTINUE:return MB_CONTINUE;
}
}
#elif CURRENT_PLATFORM == PLATFORM_MACOSX //Use Cocoa to display the message box.
int msgbox(string msg, string title, int buttons)
{
NSString* defbutton = nil;
NSString* altbutton = nil;
NSString* otherbutton = nil;
switch(buttons)
{
default:
case MB_OK:
defbutton = @"Ok";
break;
case MB_OKCANCEL:
defbutton = @"Ok";
altbutton = @"Cancel";
break;
case MB_RETRYCANCEL:
defbutton = @"Retry";
altbutton = @"Cancel";
break;
case MB_YESNO:
defbutton = @"Yes";
altbutton = @"No";
break;
case MB_YESNOCANCEL:
defbutton = @"Yes";
altbutton = @"No";
otherbutton = @"Cancel";
break;
case MB_ABORTRETRYIGNORE:
defbutton = @"Abort";
altbutton = @"Retry";
otherbutton = @"Ignore";
break;
case MB_CANCELTRYCONTINUE:
defbutton = @"Cancel";
altbutton = @"Try Again";
otherbutton = @"Continue";
break;
}
NSAlert* alert = [NSAlert alertWithMessageText:[NSString stringWithCString:title.c_str() encoding:[NSString defaultCStringEncoding]]
defaultButton:defbutton
alternateButton:altbutton
otherButton:otherbutton
informativeTextWithFormat:@"%s", msg.c_str()];
//brings this 'application' to the front.
[[NSRunningApplication currentApplication] activateWithOptions:NSApplicationActivateIgnoringOtherApps];
NSInteger retval = [alert runModal];
//Convert the NSAlert return values into my MB_* return values.
if(retval == NSAlertDefaultReturn)
{
switch(buttons)
{
case MB_OK:
case MB_OKCANCEL:
return MB_OK;
case MB_YESNO:
case MB_YESNOCANCEL:
return MB_YES;
case MB_ABORTRETRYIGNORE:
return MB_ABORT;
case MB_CANCELTRYCONTINUE:
return MB_CANCEL;
case MB_RETRYCANCEL:
return MB_RETRY;
}
} else if(retval == NSAlertAlternateReturn)
{
switch(buttons)
{
case MB_OKCANCEL:
case MB_RETRYCANCEL:
return MB_CANCEL;
case MB_YESNO:
case MB_YESNOCANCEL:
return MB_NO;
case MB_ABORTRETRYIGNORE:
return MB_RETRY;
case MB_CANCELTRYCONTINUE:
return MB_TRYAGAIN;
}
} else if(retval == NSAlertOtherReturn)
{
switch(buttons)
{
case MB_YESNOCANCEL:
return MB_CANCEL;
case MB_ABORTRETRYIGNORE:
return MB_IGNORE;
case MB_CANCELTRYCONTINUE:
return MB_CONTINUE;
}
}
return NULL;
}
#else
int msgbox(string msg, string title, int buttons)
{
//WHAT DO I DO??????
return 0;
}
//#error No implementation of message boxes on current platform!
#endif // CURRENT_PLATFORM
编辑:我不喜欢使用Qt有几个原因:它太重了,在我的主电脑上不起作用;它没有给我足够的控制权。无论如何,我正试图在不依赖其他库的情况下从头开始制作这个游戏引擎,作为一个业余项目(我最终将用自己的代码取代SDL)。
我创建了一个简单的包装器函数,该函数使用SDL 2.0中的SDL_ShowMessageBox,它取代了我提交的以前的代码,并且可以在Linux、Mac&Windows。
SDL 2.0可在(http://www.libsdl.org/tmp/download-2.0.php)。
您必须在Linux上自己构建SDL 2-只需下载所提供页面中的源代码,然后提取存档并按照install.txt中的安装说明进行操作(在构建SDL 2中,库被放在/usr/local/lib文件夹中-您可能需要移动它们或告诉链接器它们在哪里(include文件在include目录中)。
这是代码:
示例(使用我的函数):
int i = showMessageBox(mySDLWindow, "Message", "Title", 3, MB_BUTTONS("BUTTON 1", "BUTTON 2", "BUTTON 3"), 0);
printf("Button %i was pressed", i + 1);
messagebox.h:
//Cross-platform message box method.
#include <string>
#include <SDL/SDL.h> //SDL 2.0 header file
//Helper macro
#define MB_BUTTONS(...) ((char*[]) {__VA_ARGS__})
//Flexible message box function.
//Returns the index of button pressed on success or a negative value on a failure.
//The parent argument can be set to NULL if not available.
int showMessageBox(SDL_Window *parent, std::string msg, std::string title,
int count, char* buttons[], int defbutton = 0);
messagebox.cpp:
//Complex function
int showMessageBox(SDL_Window *parent, string msg, string title,
int count, char* buttons[], int defbutton)
{
//Variables.
int resultButton = 0;
SDL_MessageBoxData mbdata;
//Set the message box information.
mbdata.flags = SDL_MESSAGEBOX_INFORMATION;
mbdata.message = msg.c_str();
mbdata.title = title.c_str();
mbdata.colorScheme = NULL;
mbdata.window = parent;
mbdata.numbuttons = count;
//Allocate buttons.
SDL_MessageBoxButtonData *butarray = new SDL_MessageBoxButtonData[mbdata.numbuttons];
//Set the button values.
for(unsigned char i = 0; i < mbdata.numbuttons; i++)
{
//Is this button the default button?
if(i == defbutton)
{
butarray[i].flags = SDL_MESSAGEBOX_BUTTON_RETURNKEY_DEFAULT;
} else
{
butarray[i].flags = 0;
}
//Set button text.
if(buttons[i] != NULL)
{
butarray[i].text = buttons[i];
}
//Set button ID.
butarray[i].buttonid = i;
}
//Set the message box data's button array.
mbdata.buttons = butarray;
//Display the message box.
int retval = SDL_ShowMessageBox(&mbdata, &resultButton);
//Deallocate the buttons array to prevent memory leaks.
delete[] butarray;
//Return the result (-1 on failure or if the dialog was closed).
return retval < 0 ? -1 : resultButton;
}
我使用gdialog/kdialog并在命令行上传递消息。这是代码:
#include <cstdlib>
#include <string>
const char * getDialogCommand() {
if (::system(NULL)) {
if (::system("which gdialog") == 0)
return "gdialog";
else if (::system("which kdialog") == 0)
return "kdialog";
}
return NULL;
}
void showWarning(const std::string & warning) {
const char * dialogCommand = getDialogCommand();
if (dialogCommand) {
std::string command = dialogCommand;
command += " --title "Message Box Title" --msgbox "" + warning + """;
int result = ::system(command.c_str());
if (result == 0)
return; // success
}
// fail-safe method here, using stdio perhaps, depends on your application
}
这不是世界上最健壮的代码,但至少在我们的游戏中,我从未见过它失败。在代码方面,它是无依赖的,但您必须确保在字符串中不使用会破坏命令行的字符,即转义符,如<,>&,!\,以及所有非ASCII。
还请注意,SDL 2.0具有SDL_ShowMessageBox。