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vga: implement text mode character blink

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When bit 3 of the VGA Attribute Mode Control register is set, attribute
bit 7 switches from selecting bright background colors to enabling
character blink.

Implement this by tracking a separate blink phase timer that toggles
every 32 frames (matching real VGA hardware frame counter bit 5 @60hz),
and rendering blinking characters by replacing their foreground with
background during the off phase.

As with cursor, no VMState migration of the fields, as they are
transient display-side states.

Related to: https://gitlab.com/qemu-project/qemu/-/work_items/1585
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-ID: <20260525081944.1494798-1-marcandre.lureau@redhat.com>
This commit is contained in:
Marc-André Lureau
2026-05-25 12:19:44 +04:00
parent a9e8186be1
commit a0e5242e1c
2 changed files with 23 additions and 4 deletions
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25
hw/display/vga.c
View File

@@ -45,8 +45,10 @@
bool have_vga = true;
/* 16 state changes per vertical frame @60 Hz */
/* frame counter bit 4: cursor blink toggles every 16 frames @60 Hz */
#define VGA_TEXT_CURSOR_PERIOD_MS (1000 * 2 * 16 / 60)
/* frame counter bit 5: character blink toggles every 32 frames @60 Hz */
#define VGA_TEXT_BLINK_PERIOD_MS (1000 * 2 * 32 / 60)
/* Address mask for non-VESA modes. */
#define VGA_VRAM_SIZE (256 * KiB)
@@ -1190,7 +1192,6 @@ static void vga_get_text_resolution(VGACommonState *s, int *pwidth, int *pheight
* - double scan
* - double width
* - underline
* - flashing
*/
static void vga_draw_text(VGACommonState *s, int full_update)
{
@@ -1286,6 +1287,13 @@ static void vga_draw_text(VGACommonState *s, int full_update)
s->cursor_blink_time = now + VGA_TEXT_CURSOR_PERIOD_MS / 2;
s->cursor_visible_phase = !s->cursor_visible_phase;
}
if (now >= s->blink_time) {
s->blink_time = now + VGA_TEXT_BLINK_PERIOD_MS / 2;
s->blink_visible_phase = !s->blink_visible_phase;
if (s->ar[VGA_ATC_MODE] & 0x08) {
full_update = 1;
}
}
dest = surface_data(surface);
linesize = surface_stride(surface);
@@ -1317,8 +1325,17 @@ static void vga_draw_text(VGACommonState *s, int full_update)
#endif
font_ptr = font_base[(cattr >> 3) & 1];
font_ptr += 32 * 4 * ch;
bgcol = palette[cattr >> 4];
fgcol = palette[cattr & 0x0f];
if (s->ar[VGA_ATC_MODE] & 0x08) {
bgcol = palette[(cattr >> 4) & 0x07];
if ((cattr & 0x80) && !s->blink_visible_phase) {
fgcol = bgcol;
} else {
fgcol = palette[cattr & 0x0f];
}
} else {
bgcol = palette[cattr >> 4];
fgcol = palette[cattr & 0x0f];
}
if (cw == 16) {
vga_draw_glyph16(d1, linesize,
font_ptr, cheight, fgcol, bgcol);

2
hw/display/vga_int.h
View File

@@ -130,6 +130,8 @@ typedef struct VGACommonState {
uint8_t cursor_start, cursor_end;
bool cursor_visible_phase;
int64_t cursor_blink_time;
bool blink_visible_phase;
int64_t blink_time;
uint32_t cursor_offset;
const GraphicHwOps *hw_ops;
bool full_update_text;