src/Unix/video_vosf.h

/*
 *  video_vosf.h - Video/graphics emulation, video on SEGV signals support
 *
 *  Basilisk II (C) 1997-2001 Christian Bauer
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifndef VIDEO_VOSF_H
#define VIDEO_VOSF_H

// Note: this file is #include'd in video_x.cpp
#ifdef ENABLE_VOSF

/*
 *  Page-aligned memory allocation
 */

// Align on page boundaries
static uintptr align_on_page_boundary(uintptr size)
{
        const uint32 page_size = getpagesize();
        const uint32 page_mask = page_size - 1;
        return (size + page_mask) & ~page_mask;
}

// Allocate memory on page boundary
static void * allocate_framebuffer(uint32 size, uint8 * hint = 0)
{
        // Remind that the system can allocate at 0x00000000...
        return mmap((caddr_t)hint, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, zero_fd, 0);
}


/*
 *      Screen fault handler
 */

const uintptr INVALID_PC = (uintptr)-1;

static inline void do_handle_screen_fault(uintptr addr, uintptr pc = INVALID_PC)
{
        /* Someone attempted to write to the frame buffer. Make it writeable
         * now so that the data could actually be written. It will be made
         * read-only back in one of the screen update_*() functions.
         */
        if ((addr >= mainBuffer.memStart) && (addr < mainBuffer.memEnd)) {
                const int page  = (addr - mainBuffer.memStart) >> mainBuffer.pageBits;
                caddr_t page_ad = (caddr_t)(addr & ~(mainBuffer.pageSize - 1));
                LOCK_VOSF;
                PFLAG_SET(page);
                mprotect(page_ad, mainBuffer.pageSize, PROT_READ | PROT_WRITE);
                mainBuffer.dirty = true;
                UNLOCK_VOSF;
                return;
        }
        
        /* Otherwise, we don't know how to handle the fault, let it crash */
        fprintf(stderr, "do_handle_screen_fault: unhandled address 0x%08X", addr);
        if (pc != INVALID_PC)
                fprintf(stderr, " [IP=0x%08X]", pc);
        fprintf(stderr, "\n");
        
        signal(SIGSEGV, SIG_DFL);
}

#if defined(HAVE_SIGINFO_T)

static void Screen_fault_handler(int, siginfo_t * sip, void *)
{
        D(bug("Screen_fault_handler: ADDR=0x%08X\n", sip->si_addr));
        do_handle_screen_fault((uintptr)sip->si_addr);
}

#elif defined(HAVE_SIGCONTEXT_SUBTERFUGE)

# if defined(__i386__) && defined(__linux__)
static void Screen_fault_handler(int, struct sigcontext scs)
{
        D(bug("Screen_fault_handler: ADDR=0x%08X from IP=0x%08X\n", scs.cr2, scs.eip));
        do_handle_screen_fault((uintptr)scs.cr2, (uintptr)scs.eip);
}

# elif defined(__m68k__) && defined(__NetBSD__)

# include <m68k/frame.h>
static void Screen_fault_handler(int, int code, struct sigcontext *scp)
{
        D(bug("Screen_fault_handler: ADDR=0x%08X\n", code));
        struct sigstate {
                int ss_flags;
                struct frame ss_frame;
        };
        struct sigstate *state = (struct sigstate *)scp->sc_ap;
        uintptr fault_addr;
        switch (state->ss_frame.f_format) {
                case 7:         // 68040 access error
                        // "code" is sometimes unreliable (i.e. contains NULL or a bogus address), reason unknown
                        fault_addr = state->ss_frame.f_fmt7.f_fa;
                        break;
                default:
                        fault_addr = (uintptr)code;
                        break;
        }
        do_handle_screen_fault(fault_addr);
}

# elif defined(__powerpc__) && defined(__linux__)

static void Screen_fault_handler(int, struct sigcontext_struct *scs)
{
        D(bug("Screen_fault_handler: ADDR=0x%08X from IP=0x%08X\n", scs->regs->dar, scs->regs->nip));
        do_handle_screen_fault((uintptr)scs->regs->dar, (uintptr)scs->regs->nip);
}

# else
#  error "No suitable subterfuge for Video on SEGV signals"
# endif
#else
# error "Can't do Video on SEGV signals"
#endif


/*
 *      Screen fault handler initialization
 */

#if defined(HAVE_SIGINFO_T)
static bool Screen_fault_handler_init()
{
        // Setup SIGSEGV handler to process writes to frame buffer
        sigemptyset(&vosf_sa.sa_mask);
        vosf_sa.sa_sigaction = Screen_fault_handler;
        vosf_sa.sa_flags = SA_SIGINFO;
        return (sigaction(SIGSEGV, &vosf_sa, NULL) == 0);
}
#elif defined(HAVE_SIGCONTEXT_SUBTERFUGE)
static bool Screen_fault_handler_init()
{
        // Setup SIGSEGV handler to process writes to frame buffer
        sigemptyset(&vosf_sa.sa_mask);
        vosf_sa.sa_handler = (void (*)(int)) Screen_fault_handler;
#if !EMULATED_68K && defined(__NetBSD__)
        sigaddset(&vosf_sa.sa_mask, SIGALRM);
        vosf_sa.sa_flags = SA_ONSTACK;
#else
        vosf_sa.sa_flags = 0;
#endif
        return (sigaction(SIGSEGV, &vosf_sa, NULL) == 0);
}
#endif


/*
 *      Update display for Windowed mode and VOSF
 */

// From video_blit.cpp
extern void (*Screen_blit)(uint8 * dest, const uint8 * source, uint32 length);
extern bool Screen_blitter_init(XVisualInfo * visual_info, bool native_byte_order);

/*      How can we deal with array overrun conditions ?
        
        The state of the framebuffer pages that have been touched are maintained
        in the dirtyPages[] table. That table is (pageCount + 2) bytes long.

Terminology
        
        "Last Page" denotes the pageCount-nth page, i.e. dirtyPages[pageCount - 1].
        "CLEAR Page Guard" refers to the page following the Last Page but is always
        in the CLEAR state. "SET Page Guard" refers to the page following the CLEAR
        Page Guard but is always in the SET state.

Rough process
        
        The update routines must determine which pages have to be blitted to the
        screen. This job consists in finding the first_page that was touched.
        i.e. find the next page that is SET. Then, finding how many pages were
        touched starting from first_page. i.e. find the next page that is CLEAR.

There are two cases to check:

        - Last Page is CLEAR: find_next_page_set() will reach the SET Page Guard
        but it is beyond the valid pageCount value. Therefore, we exit from the
        update routine.
        
        - Last Page is SET: first_page equals (pageCount - 1) and
        find_next_page_clear() will reach the CLEAR Page Guard. We blit the last
        page to the screen. On the next iteration, page equals pageCount and
        find_next_page_set() will reach the SET Page Guard. We still safely exit
        from the update routine because the SET Page Guard position is greater
        than pageCount.
*/

static inline void update_display_window_vosf(void)
{
        int page = 0;
        for (;;) {
                const int first_page = find_next_page_set(page);
                if (first_page >= mainBuffer.pageCount)
                        break;

                page = find_next_page_clear(first_page);
                PFLAG_CLEAR_RANGE(first_page, page);

                // Make the dirty pages read-only again
                const int32 offset  = first_page << mainBuffer.pageBits;
                const uint32 length = (page - first_page) << mainBuffer.pageBits;
                mprotect((caddr_t)(mainBuffer.memStart + offset), length, PROT_READ);
                
                // There is at least one line to update
                const int y1 = mainBuffer.pageInfo[first_page].top;
                const int y2 = mainBuffer.pageInfo[page - 1].bottom;
                const int height = y2 - y1 + 1;
                
                const int bytes_per_row = VideoMonitor.bytes_per_row;
                const int bytes_per_pixel = VideoMonitor.bytes_per_row / VideoMonitor.x;
                int i = y1 * bytes_per_row, j;
                
                if (depth == 1) {

                        // Update the_host_buffer and copy of the_buffer
                        for (j = y1; j <= y2; j++) {
                                Screen_blit(the_host_buffer + i, the_buffer + i, VideoMonitor.x >> 3);
                                i += bytes_per_row;
                        }

                } else {

                        // Update the_host_buffer and copy of the_buffer
                        for (j = y1; j <= y2; j++) {
                                Screen_blit(the_host_buffer + i, the_buffer + i, bytes_per_pixel * VideoMonitor.x);
                                i += bytes_per_row;
                        }
                }

                if (have_shm)
                        XShmPutImage(x_display, the_win, the_gc, img, 0, y1, 0, y1, VideoMonitor.x, height, 0);
                else
                        XPutImage(x_display, the_win, the_gc, img, 0, y1, 0, y1, VideoMonitor.x, height);
        }

        mainBuffer.dirty = false;
}


/*
 *      Update display for DGA mode and VOSF
 *      (only in Direct Addressing mode)
 */

#if REAL_ADDRESSING || DIRECT_ADDRESSING
static inline void update_display_dga_vosf(void)
{
        int page = 0;
        for (;;) {
                const int first_page = find_next_page_set(page);
                if (first_page >= mainBuffer.pageCount)
                        break;

                page = find_next_page_clear(first_page);
                PFLAG_CLEAR_RANGE(first_page, page);

                // Make the dirty pages read-only again
                const int32 offset  = first_page << mainBuffer.pageBits;
                const uint32 length = (page - first_page) << mainBuffer.pageBits;
                mprotect((caddr_t)(mainBuffer.memStart + offset), length, PROT_READ);
                
                // I am sure that y2 >= y1 and depth != 1
                const int y1 = mainBuffer.pageInfo[first_page].top;
                const int y2 = mainBuffer.pageInfo[page - 1].bottom;
                
                const int bytes_per_row = VideoMonitor.bytes_per_row;
                const int bytes_per_pixel = VideoMonitor.bytes_per_row / VideoMonitor.x;
                int i, j;
                
                // Check for first column from left and first column
                // from right that have changed
                int x1 = VideoMonitor.x * bytes_per_pixel - 1;
                for (j = y1; j <= y2; j++) {
                        uint8 * const p1 = &the_buffer[j * bytes_per_row];
                        uint8 * const p2 = &the_buffer_copy[j * bytes_per_row];
                        for (i = 0; i < x1; i++) {
                                if (p1[i] != p2[i]) {
                                        x1 = i;
                                        break;
                                }
                        }
                }
                x1 /= bytes_per_pixel;
                
                int x2 = x1 * bytes_per_pixel;
                for (j = y2; j >= y1; j--) {
                        uint8 * const p1 = &the_buffer[j * bytes_per_row];
                        uint8 * const p2 = &the_buffer_copy[j * bytes_per_row];
                        for (i = VideoMonitor.x * bytes_per_pixel - 1; i > x2; i--) {
                                if (p1[i] != p2[i]) {
                                        x2 = i;
                                        break;
                                }
                        }
                }
                x2 /= bytes_per_pixel;
                
                // Update the_host_buffer and copy of the_buffer
                // There should be at least one pixel to copy
                const int width = x2 - x1 + 1;
                i = y1 * bytes_per_row + x1 * bytes_per_pixel;
                for (j = y1; j <= y2; j++) {
                        Screen_blit(the_host_buffer + i, the_buffer + i, bytes_per_pixel * width);
                        memcpy(the_buffer_copy + i, the_buffer + i, bytes_per_pixel * width);
                        i += bytes_per_row;
                }
        }
        mainBuffer.dirty = false;
}
#endif

#endif /* ENABLE_VOSF */

#endif /* VIDEO_VOSF_H */
Revision:	1.15
Committed:	2001-03-06T18:41:12Z (23 years, 8 months ago) by cebix
Content type:	text/plain
Branch:	MAIN
Changes since 1.14:	+7 -65 lines
Log Message:	added patches from Brian J. Johnson (better VOSF performance and responsiveness)
#	User	Rev	Content
1	gbeauche	1.1	/*
2			* video_vosf.h - Video/graphics emulation, video on SEGV signals support
3			*
4	gbeauche	1.13	* Basilisk II (C) 1997-2001 Christian Bauer
5	gbeauche	1.1	*
6			* This program is free software; you can redistribute it and/or modify
7			* it under the terms of the GNU General Public License as published by
8			* the Free Software Foundation; either version 2 of the License, or
9			* (at your option) any later version.
10			*
11			* This program is distributed in the hope that it will be useful,
12			* but WITHOUT ANY WARRANTY; without even the implied warranty of
13			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14			* GNU General Public License for more details.
15			*
16			* You should have received a copy of the GNU General Public License
17			* along with this program; if not, write to the Free Software
18			* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19			*/
20
21			#ifndef VIDEO_VOSF_H
22			#define VIDEO_VOSF_H
23
24			// Note: this file is #include'd in video_x.cpp
25			#ifdef ENABLE_VOSF
26
27			/*
28			* Page-aligned memory allocation
29			*/
30
31			// Align on page boundaries
32	gbeauche	1.4	static uintptr align_on_page_boundary(uintptr size)
33	gbeauche	1.1	{
34			const uint32 page_size = getpagesize();
35			const uint32 page_mask = page_size - 1;
36			return (size + page_mask) & ~page_mask;
37			}
38
39			// Allocate memory on page boundary
40			static void * allocate_framebuffer(uint32 size, uint8 * hint = 0)
41			{
42			// Remind that the system can allocate at 0x00000000...
43			return mmap((caddr_t)hint, size, PROT_READ \| PROT_WRITE, MAP_PRIVATE, zero_fd, 0);
44			}
45
46
47			/*
48			* Screen fault handler
49			*/
50
51	gbeauche	1.11	const uintptr INVALID_PC = (uintptr)-1;
52
53			static inline void do_handle_screen_fault(uintptr addr, uintptr pc = INVALID_PC)
54	gbeauche	1.1	{
55	gbeauche	1.11	/* Someone attempted to write to the frame buffer. Make it writeable
56			* now so that the data could actually be written. It will be made
57			* read-only back in one of the screen update_*() functions.
58			*/
59			if ((addr >= mainBuffer.memStart) && (addr < mainBuffer.memEnd)) {
60			const int page = (addr - mainBuffer.memStart) >> mainBuffer.pageBits;
61			caddr_t page_ad = (caddr_t)(addr & ~(mainBuffer.pageSize - 1));
62			LOCK_VOSF;
63			PFLAG_SET(page);
64			mprotect(page_ad, mainBuffer.pageSize, PROT_READ \| PROT_WRITE);
65	gbeauche	1.13	mainBuffer.dirty = true;
66	gbeauche	1.11	UNLOCK_VOSF;
67			return;
68	gbeauche	1.1	}
69
70	gbeauche	1.11	/* Otherwise, we don't know how to handle the fault, let it crash */
71			fprintf(stderr, "do_handle_screen_fault: unhandled address 0x%08X", addr);
72			if (pc != INVALID_PC)
73			fprintf(stderr, " [IP=0x%08X]", pc);
74			fprintf(stderr, "\n");
75
76			signal(SIGSEGV, SIG_DFL);
77	gbeauche	1.1	}
78
79			#if defined(HAVE_SIGINFO_T)
80	cebix	1.6
81	gbeauche	1.1	static void Screen_fault_handler(int, siginfo_t * sip, void *)
82			{
83			D(bug("Screen_fault_handler: ADDR=0x%08X\n", sip->si_addr));
84	gbeauche	1.4	do_handle_screen_fault((uintptr)sip->si_addr);
85	gbeauche	1.1	}
86	cebix	1.6
87	gbeauche	1.1	#elif defined(HAVE_SIGCONTEXT_SUBTERFUGE)
88	cebix	1.6
89	gbeauche	1.1	# if defined(__i386__) && defined(__linux__)
90			static void Screen_fault_handler(int, struct sigcontext scs)
91			{
92			D(bug("Screen_fault_handler: ADDR=0x%08X from IP=0x%08X\n", scs.cr2, scs.eip));
93	gbeauche	1.11	do_handle_screen_fault((uintptr)scs.cr2, (uintptr)scs.eip);
94	gbeauche	1.1	}
95	cebix	1.6
96			# elif defined(__m68k__) && defined(__NetBSD__)
97
98			# include <m68k/frame.h>
99			static void Screen_fault_handler(int, int code, struct sigcontext *scp)
100			{
101			D(bug("Screen_fault_handler: ADDR=0x%08X\n", code));
102			struct sigstate {
103			int ss_flags;
104			struct frame ss_frame;
105			};
106			struct sigstate state = (struct sigstate )scp->sc_ap;
107			uintptr fault_addr;
108			switch (state->ss_frame.f_format) {
109			case 7: // 68040 access error
110			// "code" is sometimes unreliable (i.e. contains NULL or a bogus address), reason unknown
111			fault_addr = state->ss_frame.f_fmt7.f_fa;
112			break;
113			default:
114			fault_addr = (uintptr)code;
115			break;
116			}
117			do_handle_screen_fault(fault_addr);
118			}
119
120	cebix	1.14	# elif defined(__powerpc__) && defined(__linux__)
121
122			static void Screen_fault_handler(int, struct sigcontext_struct *scs)
123			{
124			D(bug("Screen_fault_handler: ADDR=0x%08X from IP=0x%08X\n", scs->regs->dar, scs->regs->nip));
125			do_handle_screen_fault((uintptr)scs->regs->dar, (uintptr)scs->regs->nip);
126			}
127
128	gbeauche	1.1	# else
129			# error "No suitable subterfuge for Video on SEGV signals"
130			# endif
131			#else
132			# error "Can't do Video on SEGV signals"
133			#endif
134
135
136			/*
137			* Screen fault handler initialization
138			*/
139
140			#if defined(HAVE_SIGINFO_T)
141			static bool Screen_fault_handler_init()
142			{
143			// Setup SIGSEGV handler to process writes to frame buffer
144			sigemptyset(&vosf_sa.sa_mask);
145			vosf_sa.sa_sigaction = Screen_fault_handler;
146	cebix	1.5	vosf_sa.sa_flags = SA_SIGINFO;
147	gbeauche	1.1	return (sigaction(SIGSEGV, &vosf_sa, NULL) == 0);
148			}
149			#elif defined(HAVE_SIGCONTEXT_SUBTERFUGE)
150			static bool Screen_fault_handler_init()
151			{
152			// Setup SIGSEGV handler to process writes to frame buffer
153			sigemptyset(&vosf_sa.sa_mask);
154			vosf_sa.sa_handler = (void (*)(int)) Screen_fault_handler;
155	cebix	1.7	#if !EMULATED_68K && defined(__NetBSD__)
156			sigaddset(&vosf_sa.sa_mask, SIGALRM);
157			vosf_sa.sa_flags = SA_ONSTACK;
158			#else
159	gbeauche	1.1	vosf_sa.sa_flags = 0;
160	cebix	1.7	#endif
161	gbeauche	1.1	return (sigaction(SIGSEGV, &vosf_sa, NULL) == 0);
162			}
163			#endif
164
165
166			/*
167			* Update display for Windowed mode and VOSF
168			*/
169
170	gbeauche	1.13	// From video_blit.cpp
171			extern void (Screen_blit)(uint8 dest, const uint8 * source, uint32 length);
172			extern bool Screen_blitter_init(XVisualInfo * visual_info, bool native_byte_order);
173
174	gbeauche	1.12	/* How can we deal with array overrun conditions ?
175
176			The state of the framebuffer pages that have been touched are maintained
177			in the dirtyPages[] table. That table is (pageCount + 2) bytes long.
178
179			Terminology
180
181			"Last Page" denotes the pageCount-nth page, i.e. dirtyPages[pageCount - 1].
182			"CLEAR Page Guard" refers to the page following the Last Page but is always
183			in the CLEAR state. "SET Page Guard" refers to the page following the CLEAR
184			Page Guard but is always in the SET state.
185
186			Rough process
187
188	gbeauche	1.13	The update routines must determine which pages have to be blitted to the
189	gbeauche	1.12	screen. This job consists in finding the first_page that was touched.
190			i.e. find the next page that is SET. Then, finding how many pages were
191			touched starting from first_page. i.e. find the next page that is CLEAR.
192
193	gbeauche	1.13	There are two cases to check:
194	gbeauche	1.12
195			- Last Page is CLEAR: find_next_page_set() will reach the SET Page Guard
196			but it is beyond the valid pageCount value. Therefore, we exit from the
197			update routine.
198
199			- Last Page is SET: first_page equals (pageCount - 1) and
200			find_next_page_clear() will reach the CLEAR Page Guard. We blit the last
201			page to the screen. On the next iteration, page equals pageCount and
202			find_next_page_set() will reach the SET Page Guard. We still safely exit
203			from the update routine because the SET Page Guard position is greater
204			than pageCount.
205			*/
206
207	gbeauche	1.1	static inline void update_display_window_vosf(void)
208			{
209			int page = 0;
210			for (;;) {
211	gbeauche	1.11	const int first_page = find_next_page_set(page);
212			if (first_page >= mainBuffer.pageCount)
213	gbeauche	1.1	break;
214	gbeauche	1.11
215			page = find_next_page_clear(first_page);
216			PFLAG_CLEAR_RANGE(first_page, page);
217	cebix	1.7
218	gbeauche	1.1	// Make the dirty pages read-only again
219			const int32 offset = first_page << mainBuffer.pageBits;
220			const uint32 length = (page - first_page) << mainBuffer.pageBits;
221			mprotect((caddr_t)(mainBuffer.memStart + offset), length, PROT_READ);
222
223			// There is at least one line to update
224			const int y1 = mainBuffer.pageInfo[first_page].top;
225			const int y2 = mainBuffer.pageInfo[page - 1].bottom;
226			const int height = y2 - y1 + 1;
227
228			const int bytes_per_row = VideoMonitor.bytes_per_row;
229			const int bytes_per_pixel = VideoMonitor.bytes_per_row / VideoMonitor.x;
230	cebix	1.15	int i = y1 * bytes_per_row, j;
231	gbeauche	1.1
232	cebix	1.6	if (depth == 1) {
233
234			// Update the_host_buffer and copy of the_buffer
235			for (j = y1; j <= y2; j++) {
236	cebix	1.15	Screen_blit(the_host_buffer + i, the_buffer + i, VideoMonitor.x >> 3);
237	cebix	1.6	i += bytes_per_row;
238			}
239
240			} else {
241
242			// Update the_host_buffer and copy of the_buffer
243			for (j = y1; j <= y2; j++) {
244	cebix	1.15	Screen_blit(the_host_buffer + i, the_buffer + i, bytes_per_pixel * VideoMonitor.x);
245	cebix	1.6	i += bytes_per_row;
246			}
247	gbeauche	1.1	}
248	cebix	1.15
249	gbeauche	1.1	if (have_shm)
250	cebix	1.15	XShmPutImage(x_display, the_win, the_gc, img, 0, y1, 0, y1, VideoMonitor.x, height, 0);
251	gbeauche	1.1	else
252	cebix	1.15	XPutImage(x_display, the_win, the_gc, img, 0, y1, 0, y1, VideoMonitor.x, height);
253	gbeauche	1.1	}
254	cebix	1.15
255	gbeauche	1.13	mainBuffer.dirty = false;
256	gbeauche	1.1	}
257
258
259			/*
260			* Update display for DGA mode and VOSF
261			* (only in Direct Addressing mode)
262			*/
263
264			#if REAL_ADDRESSING \|\| DIRECT_ADDRESSING
265			static inline void update_display_dga_vosf(void)
266			{
267			int page = 0;
268			for (;;) {
269	gbeauche	1.11	const int first_page = find_next_page_set(page);
270			if (first_page >= mainBuffer.pageCount)
271	gbeauche	1.1	break;
272	gbeauche	1.11
273			page = find_next_page_clear(first_page);
274			PFLAG_CLEAR_RANGE(first_page, page);
275
276	gbeauche	1.1	// Make the dirty pages read-only again
277			const int32 offset = first_page << mainBuffer.pageBits;
278			const uint32 length = (page - first_page) << mainBuffer.pageBits;
279			mprotect((caddr_t)(mainBuffer.memStart + offset), length, PROT_READ);
280
281			// I am sure that y2 >= y1 and depth != 1
282			const int y1 = mainBuffer.pageInfo[first_page].top;
283			const int y2 = mainBuffer.pageInfo[page - 1].bottom;
284
285			const int bytes_per_row = VideoMonitor.bytes_per_row;
286			const int bytes_per_pixel = VideoMonitor.bytes_per_row / VideoMonitor.x;
287			int i, j;
288
289			// Check for first column from left and first column
290			// from right that have changed
291			int x1 = VideoMonitor.x * bytes_per_pixel - 1;
292			for (j = y1; j <= y2; j++) {
293			uint8 * const p1 = &the_buffer[j * bytes_per_row];
294			uint8 * const p2 = &the_buffer_copy[j * bytes_per_row];
295			for (i = 0; i < x1; i++) {
296			if (p1[i] != p2[i]) {
297			x1 = i;
298			break;
299			}
300			}
301			}
302			x1 /= bytes_per_pixel;
303
304			int x2 = x1 * bytes_per_pixel;
305			for (j = y2; j >= y1; j--) {
306			uint8 * const p1 = &the_buffer[j * bytes_per_row];
307			uint8 * const p2 = &the_buffer_copy[j * bytes_per_row];
308			for (i = VideoMonitor.x * bytes_per_pixel - 1; i > x2; i--) {
309			if (p1[i] != p2[i]) {
310			x2 = i;
311			break;
312			}
313			}
314			}
315			x2 /= bytes_per_pixel;
316
317			// Update the_host_buffer and copy of the_buffer
318			// There should be at least one pixel to copy
319			const int width = x2 - x1 + 1;
320			i = y1 * bytes_per_row + x1 * bytes_per_pixel;
321			for (j = y1; j <= y2; j++) {
322	gbeauche	1.13	Screen_blit(the_host_buffer + i, the_buffer + i, bytes_per_pixel * width);
323	gbeauche	1.1	memcpy(the_buffer_copy + i, the_buffer + i, bytes_per_pixel * width);
324			i += bytes_per_row;
325			}
326			}
327	gbeauche	1.13	mainBuffer.dirty = false;
328	gbeauche	1.1	}
329			#endif
330
331			#endif /* ENABLE_VOSF */
332
333			#endif /* VIDEO_VOSF_H */