giz dblbuff, scanline mode

git-svn-id: file:///home/notaz/opt/svn/PicoDrive/platform@270 be3aeb3a-fb24-0410-a615-afba39da0efa

base_readme.txt

@@ -132,11 +132,10 @@ graphics problems for some games, so it's best to use 16bit one.
 #endif
 
 #ifdef GIZ
-@@0. "Interlaced rendering"
+@@0. "Scanline mode"
 This option was designed to work around slow framebuffer access (the Gizmondo's
-main bottleneck) by drawing every other line (odd numbered lines during odd
-numbered frames and even numbered lines during even frames). This improves
-performance greatly, but introduces artifacts for fast scrolling games.
+main bottleneck) by drawing every other line (even nummbered lines only).
+This improves performance greatly, but looses detail.
 
 #endif
 #ifdef GP2X
@@ -272,10 +271,14 @@ game to get sound. This is because most games initialize sound chips on
 startup, and this data is lost when sound chips are being enabled/disabled.
 
 #ifdef GIZ
+@@1. "Double buffering"
+Draws the display to offscreen buffer, and flips it with visible one when done.
+Unfortunately this causes serious tearing, unless v-sync is used (next option).
+
 @@1. "Wait for V-sync"
-Waits for vertical sync before drawing. This option doesn't eliminate tearing
-problems, because full framebuffer update takes much more time then the blanking
-period lasts on Gizmondo..
+Waits for vertical sync before drawing (or flipping buffers, if previous option
+is enabled). Emulation is stopped while waiting, so this causes large performance
+hit.
 
 #endif
 @@1. "gzip savestates"

common/emu.h

@@ -8,7 +8,7 @@ typedef struct {
 	int EmuOpt;		// LSb->MSb: use_sram, show_fps, enable_sound, gzip_saves,
 					// squidgehack, no_save_cfg_on_exit, <unused>, 16_bit_mode
 					// craigix_ram, confirm_save, show_cd_leds, confirm_load
-					// A_SNs_gamma, perfect_vsync, interlace
+					// A_SNs_gamma, perfect_vsync, giz_scanlines, giz_dblbuff
 	int PicoOpt;  // used for config saving only, see Pico.h
 	int PsndRate; // ditto
 	int PicoRegion; // ditto

common/menu.h

@@ -53,6 +53,7 @@ typedef enum
 	MA_OPT_INTERLACED,	/* giz */
 	MA_OPT2_GAMMA,
 	MA_OPT2_A_SN_GAMMA,
+	MA_OPT2_DBLBUFF,	/* giz */
 	MA_OPT2_VSYNC,
 	MA_OPT2_ENABLE_Z80,
 	MA_OPT2_ENABLE_YM2612,