Right. al_ref_ustr is the thing to use; and I've worked around the variable declaration problem by putting a bunch of braces all over the place.
I've now finished what I was trying to implement; but I'm pretty disappointed with how it turned out. It doesn't really look 'native' at all. It looks like quite bad. 
{"name":"606671","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/b\/a\/ba6f742214ab05bcfd8921e98b5d9082.png","w":466,"h":188,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/b\/a\/ba6f742214ab05bcfd8921e98b5d9082"}
I assumed that if I didn't specify a font, Windows would automatically pick whatever the normal font is – but unfortunately it actually just uses a trashy looking system font.
Also, my current implementation doesn't make any attempt to make the box big enough to fit the text. The height of the box is the same regardless of the text.
So.. I guess the main shortcomings of my implementation are as follows:
The height of the box is not set dynamically, and so long messages may appear underneath the buttons or be truncated.
The size of the buttons is not set dynamically, and so long button names might not fit.
The text is missing the white background that standard dialog boxes have.
Flags such as ALLEGRO_MESSAGEBOX_WARN and ALLEGRO_MESSAGEBOX_ERROR are ignored. (These flags should have a corresponding sound-effect, and an icon inside the dialog box.)
... So the result is pretty ugly, but at least it has the correct buttons!
I'm not intending to work on this again in the near future, but if someone else wants to have a go at it, or if you think this is good enough to put into Allegro, then here's the code:
#SelectExpand
1// DialogProc callback for customized windows dialog boxes
2INT_PTR CALLBACK _al_winAPI_DlgProc
(HWND hwnd, UINT wm, WPARAM wParam, LPARAM lParam
)
3{
4 (void)lParam
; // unused
5 if (wm
== WM_INITDIALOG
)
6 return TRUE
;
7 if (wm
== WM_COMMAND
)
8 {
9 int control_id
= LOWORD
(wParam
);
10
11 if (control_id
> 1000)
12 {
13 EndDialog
(hwnd, control_id-1000
);
14 return TRUE
;
15 }
16 }
17 return FALSE
;
18}
19
20int _al_show_native_message_box
(ALLEGRO_DISPLAY *display,
21 ALLEGRO_NATIVE_DIALOG
*fd
)
22{
23 /* heading + text are combined together */
24
25 if (al_ustr_size(fd->mb_heading
))
26 al_ustr_append_cstr(fd->mb_heading,
"\n\n");
27
28 al_ustr_append(fd->mb_heading, fd->mb_text
);
29
30 // If there are no custom button names, then we can use a standard Windows message box.
31 if (!fd->mb_buttons
|| (fd->flags
& (ALLEGRO_MESSAGEBOX_OK_CANCEL
| ALLEGRO_MESSAGEBOX_YES_NO
)))
32 {
33 UINT type
= 0;
34 int result
;
35
36 uint16_t *wide_text,
*wide_title
;
37 size_t text_len, title_len
;
38
39 /* Note: the message box code cannot assume that Allegro is installed. */
40
41 if (fd->flags
& ALLEGRO_MESSAGEBOX_QUESTION
)
42 type
|= MB_ICONQUESTION
;
43 else if (fd->flags
& ALLEGRO_MESSAGEBOX_WARN
)
44 type
|= MB_ICONWARNING
;
45 else if (fd->flags
& ALLEGRO_MESSAGEBOX_ERROR
)
46 type
|= MB_ICONERROR
;
47 else
48 type
|= MB_ICONINFORMATION
;
49
50 if (fd->flags
& ALLEGRO_MESSAGEBOX_YES_NO
)
51 type
|= MB_YESNO
;
52 else if (fd->flags
& ALLEGRO_MESSAGEBOX_OK_CANCEL
)
53 type
|= MB_OKCANCEL
;
54
55 text_len
= al_ustr_size_utf16(fd->mb_heading
);
56 title_len
= al_ustr_size_utf16(fd->title
);
57
58 wide_text
= al_malloc(text_len
+ 1);
59 if (!wide_text
)
60 return 0;
61
62 wide_title
= al_malloc(title_len
+ 1);
63 if (!wide_title
) {
64 al_free(wide_text
);
65 return 0;
66 }
67
68 al_ustr_encode_utf16(fd->mb_heading, wide_text, text_len
);
69 al_ustr_encode_utf16(fd->title, wide_title, title_len
);
70
71 result
= MessageBoxW
(al_get_win_window_handle(display
),
72 (LPCWSTR
) wide_text,
(LPCWSTR
) wide_title, type
);
73
74 al_free(wide_text
);
75 al_free(wide_title
);
76
77 if (result
== IDYES
|| result
== IDOK
)
78 return 1;
79 else
80 return 0;
81 }
82 // else there are custom buttons - so things are more complex
83 else
84 {
85 size_t text_size
= al_ustr_size_utf16(fd->mb_heading
);
86 size_t title_size
= al_ustr_size_utf16(fd->title
);
87
88 size_t num_buttons
;
89 int* button_caption_start
;
90 int* button_caption_end
;
91
92 // count the number of custom buttons
93 {
94 int offset
= 0;
95 num_buttons
= 0;
96 do
97 {
98 offset
= al_ustr_find_chr(fd->mb_buttons, offset,
'|');
99 al_ustr_next(fd->mb_buttons,
&offset
);
100 num_buttons
++;
101 } while (offset
> 0);
102 }
103 ASSERT(num_buttons
> 0);
104
105 // record the start and end of each button name
106 button_caption_start
= al_malloc(sizeof(*button_caption_start
)*num_buttons
);
107 button_caption_end
= al_malloc(sizeof(*button_caption_end
)*num_buttons
);
108 if (!button_caption_start
|| !button_caption_end
)
109 {
110 // failed to allocate memory for at least one of the arrays
111 al_free(button_caption_start
);
112 al_free(button_caption_end
);
113 return 0;
114 }
115
116 // record the start and end of each button name
117 {
118 int offset
= 0;
119 num_buttons
= 0;
120 do
121 {
122 button_caption_start
[num_buttons
] = offset
;
123 offset
= al_ustr_find_chr(fd->mb_buttons, offset,
'|');
124 button_caption_end
[num_buttons
] = offset
;
125 al_ustr_next(fd->mb_buttons,
&offset
);
126 num_buttons
++;
127 } while (offset
> 0);
128 button_caption_end
[num_buttons-1
] = al_ustr_size(fd->mb_buttons
);
129 }
130
131 {
132 // Note: the sizes of the buttons, and text box, and the dialog itself are currently mostly just arbitrary numbers.
133 // Ideally these sizes should be calculated to best suit the content of the dialog.
134 const short button_width
= 50;
135 const short button_height
= 14;
136 short dlg_width
= 200 > 20+num_buttons
*(button_width
+20) ?
200 : 20+num_buttons
*(button_width
+20);
137 short dlg_height
= 80;
138
139 //
140 int result
;
141 size_t i
; // generic iterator
142 DLGTEMPLATE
* dlg_template
;
143 BYTE
* buffer
;
144 size_t dlg_buffer_size
= sizeof(DLGTEMPLATE
);
145 dlg_buffer_size
+= 2*sizeof(WORD
); // menu and class (unused)
146 dlg_buffer_size
+= title_size
; // dialog title
147
148 // text (heading and text combined)
149 dlg_buffer_size
+= (sizeof(DWORD
) - dlg_buffer_size %
sizeof(DWORD
)) %
sizeof(DWORD
); // align to DWORD
150
151 // item data
152 dlg_buffer_size
+= sizeof(DLGITEMTEMPLATE
);
153 dlg_buffer_size
+= sizeof(DWORD
); // class
154 dlg_buffer_size
+= text_size
; // the text itself
155 dlg_buffer_size
+= sizeof(WORD
); // creation data
156
157 // similarly for each of the buttons.
158 for (i
= 0; i
< num_buttons
; i
++)
159 {
160 dlg_buffer_size
+= (sizeof(DWORD
) - dlg_buffer_size %
sizeof(DWORD
)) %
sizeof(DWORD
); // align to DWORD
161
162 // add the data size of this button
163 dlg_buffer_size
+= sizeof(DLGITEMTEMPLATE
);
164 dlg_buffer_size
+= sizeof(DWORD
); // class
165 // caption
166 {
167 ALLEGRO_USTR_INFO str_info
;
168 const ALLEGRO_USTR* sub_string
= al_ref_ustr(&str_info, fd->mb_buttons, button_caption_start
[i
], button_caption_end
[i
]);
169 size_t caption_size
= al_ustr_size_utf16(sub_string
);
170 dlg_buffer_size
+= caption_size
;
171 }
172 dlg_buffer_size
+= sizeof(WORD
); // creation data
173 }
174
175 dlg_template
= al_malloc(dlg_buffer_size
);
176 if (!dlg_template
)
177 {
178 // Not enough memory. :(
179 al_free(button_caption_start
);
180 al_free(button_caption_end
);
181 return 0;
182 }
183 dlg_template->x
= 0;
184 dlg_template->y
= 0;
185 dlg_template->cx
= dlg_width
;
186 dlg_template->cy
= dlg_height
;
187 dlg_template->cdit
= 1 + num_buttons
; // components = text + number of buttons (todo + icons for warning / error etc)
188 dlg_template->style
= DS_CENTER
| DS_MODALFRAME
| WS_CAPTION
| WS_POPUP
| WS_BORDER
;
189 dlg_template->dwExtendedStyle
= 0;
190
191 buffer
= (BYTE
*)dlg_template
;
192 buffer
+= sizeof(DLGTEMPLATE
);
193 *(WORD
*)buffer
= 0; // menu (none)
194 buffer
+= sizeof(WORD
);
195 *(WORD
*)buffer
= 0; // class (none)
196 buffer
+= sizeof(WORD
);
197 al_ustr_encode_utf16(fd->title,
(uint16_t*)buffer, title_size
); // title
198 buffer
+= title_size
;
199
200 // dialog header complete. Now for the dialog items.
201 // First, the text.
202 buffer
+= (sizeof(DWORD
) - (buffer
- (BYTE
*)dlg_template
) %
sizeof(DWORD
)) %
sizeof(DWORD
); // align to DWORD
203 {
204 DLGITEMTEMPLATE
* item
= (DLGITEMTEMPLATE
*)(buffer
);
205 item->dwExtendedStyle
= 0;
206 item->style
= WS_CHILD
| WS_VISIBLE
;
207 item->x
= 7;
208 item->y
= 7;
209 item->cx
= dlg_width
- 14;
210 item->cy
= dlg_height-7-button_height-7
;
211 item->id
= -1;
212 }
213 buffer
+= sizeof(DLGITEMTEMPLATE
);
214
215 *(WORD
*)buffer
= 0xFFFF; // pre-defined type to follow
216 *(WORD
*)(buffer
+sizeof(WORD
)) = 0x0082; // 'static'
217 buffer
+= 2*sizeof(WORD
);
218
219 al_ustr_encode_utf16(fd->mb_heading,
(uint16_t*)buffer, text_size
); // text body
220 buffer
+= text_size
;
221 *(WORD
*)buffer
= 0; // creation data (whatever that means - we don't need it)
222 buffer
+= sizeof(WORD
);
223
224 // Next, each of the buttons.
225 for (i
= 0; i
< num_buttons
; i
++)
226 {
227 buffer
+= (sizeof(DWORD
) - (buffer
- (BYTE
*)dlg_template
) %
sizeof(DWORD
)) %
sizeof(DWORD
); // align to DWORD
228 {
229 DLGITEMTEMPLATE
* item
= (DLGITEMTEMPLATE
*)buffer
;
230 item->dwExtendedStyle
= 0;
231 item->style
= WS_CHILD
| WS_VISIBLE
| WS_TABSTOP
| BS_DEFPUSHBUTTON
| (i
== 0 ? WS_GROUP
: 0);
232 item->x
= dlg_width
- (num_buttons
- i
) * (button_width
+20);
233 item->y
= dlg_height
- button_height
- 7;
234 item->cx
= button_width
;
235 item->cy
= button_height
;
236 item->id
= 1000 + i
+ 1;
237 // Note: item id will determine dialog return value. See _al_winAPI_DlgProc.
238 }
239 buffer
+= sizeof(DLGITEMTEMPLATE
);
240
241 *(WORD
*)buffer
= 0xFFFF; // pre-defined type to follow
242 *(WORD
*)(buffer
+sizeof(WORD
)) = 0x0080; // 'button'
243 buffer
+= 2*sizeof(WORD
);
244
245 // caption
246 {
247 ALLEGRO_USTR_INFO str_info
;
248 const ALLEGRO_USTR* sub_string
= al_ref_ustr(&str_info, fd->mb_buttons, button_caption_start
[i
], button_caption_end
[i
]);
249 size_t caption_size
= al_ustr_size_utf16(sub_string
);
250
251 al_ustr_encode_utf16(sub_string,
(uint16_t*)buffer, caption_size
);
252 buffer
+= caption_size
;
253 }
254 *(WORD
*)buffer
= 0;
255 buffer
+= sizeof(WORD
);
256 }
257 ASSERT(buffer
- (BYTE
*)dlg_template
== (int)dlg_buffer_size
);
258 result
= DialogBoxIndirect
(0, dlg_template,
al_get_win_window_handle(display
), _al_winAPI_DlgProc
);
259 al_free(dlg_template
);
260 al_free(button_caption_start
);
261 al_free(button_caption_end
);
262 return result
== -1 ?
0 : result
;
263 }
264 }
265}
Unless someone wants to make a better version, I think that this version should be put into Allegro so that at least then the function will do what the manual says it should do. The previous Allegro functionality for the cases without custom buttons is unchanged, so this ugliness wouldn't be a regression.
[edit]
In case anyone is interested in fixing the font problem, I think this is a good place to start. If no one else wants to look at it, I may tackle it again at some point in the future; but for the time being I'm just going to leave it alone. -- I only wanted to use these dialog boxes for debugging anyway...
]]>
. The only thing I haven't fixed is the topic of this very thread. I use MinGW myself but I may be using VC++ more for Windows 8 stuff. If I have the money to buy a Windows 8 license I intend to "port" Allegro to it (meaning have it feel like a real Windows 8 app with metro and all that, not just a compatibility app, ready for the Windows store etc.)
