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Merged
wizzomafizzo merged 3 commits into from
Aug 17, 2026
Merged

fix(zaparoo): stabilize frontend framebuffer scaling #15

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a9d319c
fix(zaparoo): settle HDMI mode before frontend spawn
wizzomafizzo Aug 16, 2026
028bf65
fix(zaparoo): avoid delayed framebuffer geometry reset
wizzomafizzo Aug 17, 2026
6ed555b
fix(video): account for pixel repetition in fb scaling
wizzomafizzo Aug 17, 2026
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92 changes: 73 additions & 19 deletions support/zaparoo/alt_launcher.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,10 @@
#include "user_io.h"
#include "video.h"

// video_reinit() is intentionally internal to upstream's video module. The
// launcher uses it only for a bounded startup retry after video_init().
extern void video_reinit();

static const char s_launcher_path[] = "zaparoo/frontend";

void alt_launcher_cfg_apply(void)
Expand Down Expand Up @@ -94,6 +98,9 @@ static pid_t s_pid = 0;
static int s_crash_count = 0;
static unsigned long s_respawn_timer = 0;
static unsigned long s_native_fb_mode_timer = 0;
static unsigned long s_hdmi_fb_reassert_timer = 0;
static int s_hdmi_fb_reasserts_remaining = 0;
static unsigned long s_hdmi_edid_retry_timer = 0;
static unsigned long s_tty_deadline = 0;
static unsigned long s_native_crt_finish_timer = 0;
static bool s_gave_up = false;
Expand Down Expand Up @@ -381,6 +388,9 @@ static void return_to_normal_mode(void)
else video_fb_enable(0);
s_native_crt = false;
s_respawn_timer = 0;
s_hdmi_fb_reassert_timer = 0;
s_hdmi_fb_reasserts_remaining = 0;
s_hdmi_edid_retry_timer = 0;
s_crash_count = 0;
s_gave_up = true;
s_escaped = true;
Expand All @@ -392,6 +402,9 @@ static void reset_launcher_state(void)
s_respawn_timer = 0;
s_tty_deadline = 0;
s_native_fb_mode_timer = 0;
s_hdmi_fb_reassert_timer = 0;
s_hdmi_fb_reasserts_remaining = 0;
s_hdmi_edid_retry_timer = 0;
s_native_crt_finish_timer = 0;
s_crash_count = 0;
s_gave_up = false;
Expand Down Expand Up @@ -437,6 +450,8 @@ static void wait_launcher_stopped(pid_t pid)

static void release_launcher_video(void)
{
s_hdmi_fb_reassert_timer = 0;
s_hdmi_fb_reasserts_remaining = 0;
if (s_native_crt)
{
s_native_crt = false;
Expand Down Expand Up @@ -519,7 +534,18 @@ static void finalize_spawn(void)
s_tty_deadline = 0;
switch_to_vt(s_vt);
if (!s_native_crt)
video_fb_enable(1);
{
// The frontend configures /dev/fb0 before Qt starts. Only publish its
// existing buffer here; rewriting the mode after Qt has painted clears
// the frame and leaves black until each region becomes dirty again.
video_fb_reassert();
// Returning to the menu can keep settling its video mode after the
// frontend is already ready. Re-assert across that init window so a
// late reset cannot leave a live framebuffer behind menu static.
s_hdmi_fb_reasserts_remaining = 5;
s_hdmi_fb_reassert_timer = GetTimer(1000);
if (!s_hdmi_fb_reassert_timer) s_hdmi_fb_reassert_timer = 1;
}
else
input_switch(0);

Expand Down Expand Up @@ -548,6 +574,12 @@ static void spawn(void)
}
else
{
// Accept the child's pre-Qt vmode request deterministically. Enabling only
// from finalize_spawn races the child: video_cmd ignores fb_cmd while the
// HPS framebuffer is disabled. Re-assert without scheduling the launcher's
// current geometry back into the kernel; that delayed write can otherwise
// overwrite the child's smaller framebuffer after Qt has mapped it.
video_fb_reassert();
printf("alt_launcher: HPS framebuffer path enabled\n");
}

Expand Down Expand Up @@ -585,7 +617,7 @@ bool alt_launcher_console_lease_active(void)

bool alt_launcher_scheduler_sleep_enabled(void)
{
return s_pid || s_init_pending || s_respawn_timer || s_tty_deadline || s_native_crt_finish_timer || s_native_fb_mode_timer;
return s_pid || s_init_pending || s_respawn_timer || s_tty_deadline || s_native_crt_finish_timer || s_native_fb_mode_timer || s_hdmi_fb_reassert_timer || s_hdmi_edid_retry_timer;
}

bool alt_launcher_native_crt(void)
Expand All @@ -601,21 +633,15 @@ void alt_launcher_init(bool native_crt)
s_respawn_timer = 0;
s_tty_deadline = 0;
s_native_crt = native_crt;
// user_io can request the launcher before video_init() has read EDID and
// selected the HDMI mode. Defer the child until that setup returns. If the
// first EDID read missed a slow monitor, allow one bounded retry after the
// link has had another 500 ms to settle.
s_hdmi_edid_retry_timer = native_crt ? 0 : GetTimer(500);
if (!native_crt && !s_hdmi_edid_retry_timer) s_hdmi_edid_retry_timer = 1;
s_init_pending = true;
}

static void alt_launcher_start(bool native_crt)
{
if (!alt_launcher_configured() || s_pid || s_gave_up)
return;
s_crash_count = 0;
s_respawn_timer = 0;
s_tty_deadline = 0;
s_native_crt = native_crt;
s_init_pending = false;
spawn();
}

void alt_launcher_prepare_for_script(void)
{
reset_launcher_tty();
Expand Down Expand Up @@ -766,11 +792,30 @@ void alt_launcher_poll(void)
s_native_fb_mode_timer = 0;
}

if (!s_native_crt && s_hdmi_fb_reassert_timer && CheckTimer(s_hdmi_fb_reassert_timer))
{
// Re-send scanout state without reconfiguring /dev/fb0 under Qt;
// resetting the live kernel framebuffer clears it until dirty repaint.
video_fb_reassert();
if (--s_hdmi_fb_reasserts_remaining > 0)
{
s_hdmi_fb_reassert_timer = GetTimer(2000);
if (!s_hdmi_fb_reassert_timer) s_hdmi_fb_reassert_timer = 1;
}
else
{
s_hdmi_fb_reassert_timer = 0;
}
printf("alt_launcher: HPS framebuffer path re-asserted (%d remaining)\n", s_hdmi_fb_reasserts_remaining);
}

int status;
if (waitpid(s_pid, &status, WNOHANG) == s_pid)
{
s_pid = 0;
s_tty_deadline = 0;
s_hdmi_fb_reassert_timer = 0;
s_hdmi_fb_reasserts_remaining = 0;
user_io_osd_key_enable(1);
bool exited = WIFEXITED(status);
int exit_status = exited ? WEXITSTATUS(status) : 0;
Expand Down Expand Up @@ -832,6 +877,13 @@ void alt_launcher_poll(void)

if (s_init_pending)
{
if (!s_native_crt && video_get_edid(NULL, NULL) == 0)
{
if (s_hdmi_edid_retry_timer && !CheckTimer(s_hdmi_edid_retry_timer)) return;
printf("alt_launcher: retrying EDID before frontend spawn\n");
video_reinit();
}
s_hdmi_edid_retry_timer = 0;
s_init_pending = false;
spawn();
return;
Expand Down Expand Up @@ -952,20 +1004,22 @@ void zaparoo_alt_launcher_init_for_core(void)
}
}

static void zaparoo_alt_launcher_prepare_menu_state(bool start)
static void zaparoo_alt_launcher_prepare_menu_state(void)
{
bool crt = load_persisted_native_crt();
printf("alt_launcher: initializing menu frontend (persisted crt=%d)\n", crt);
if (start) alt_launcher_start(crt);
else alt_launcher_init(crt);
alt_launcher_init(crt);
}

void zaparoo_alt_launcher_init_for_menu(void)
{
zaparoo_alt_launcher_prepare_menu_state(false);
zaparoo_alt_launcher_prepare_menu_state();
}

void zaparoo_alt_launcher_start_for_menu(void)
{
zaparoo_alt_launcher_prepare_menu_state(true);
// This hook runs before video_init(). Queue startup instead of forking
// immediately so EDID-selected output geometry is final before the frontend
// asks Main to choose a full or half framebuffer.
zaparoo_alt_launcher_prepare_menu_state();
}
43 changes: 39 additions & 4 deletions video.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3420,7 +3420,7 @@ static void fb_write_module_params()
});
}

void video_fb_enable(int enable, int n)
static void video_fb_set(int enable, int n, int update_module)
{
PROFILE_FUNCTION();

Expand Down Expand Up @@ -3462,7 +3462,7 @@ void video_fb_enable(int enable, int n)
//printf("Linux frame buffer: %dx%d, stride = %d bytes\n", fb_width, fb_height, fb_width * 4);
if (!fb_num)
{
fb_write_module_params();
if (update_module) fb_write_module_params();
input_switch(0);
}
else
Expand Down Expand Up @@ -3491,6 +3491,36 @@ void video_fb_enable(int enable, int n)
}
}

void video_fb_enable(int enable, int n)
{
video_fb_set(enable, n, 1);
}

void video_fb_reassert()
{
int fmt, rb, width, height, stride;
FILE *fp = fopen("/sys/module/MiSTer_fb/parameters/mode", "rt");
int fields = fp ? fscanf(fp, "%d %d %d %d %d", &fmt, &rb, &width, &height, &stride) : 0;
if (fp) fclose(fp);

if (fields == 5 && fmt == 8888 && rb == 1 && width > 0 && height > 0 && stride == width * 4)
{
// vmode may resize the launcher's live buffer after video_fb_config().
// Re-assert the kernel module's current RGB32 geometry, not stale menu geometry.
int configured_width = fb_width;
int configured_height = fb_height;
fb_width = width;
fb_height = height;
video_fb_set(1, 0, 0);
fb_width = configured_width;
fb_height = configured_height;
}
else
{
video_fb_set(1, 0, 0);
}
}

int video_fb_state()
{
if (is_menu())
Expand Down Expand Up @@ -4136,8 +4166,12 @@ void video_cmd(char *cmd)
{
if (div >= 1 && div <= 4)
{
// Pixel repetition doubles the physical output width while hact
// remains the logical source width. Apply the matching extra
// vertical divisor so the framebuffer keeps the output aspect.
int vdiv = div * (v_cur.param.pr ? 2 : 1);
width = v_cur.item[1] / div;
height = v_cur.item[5] / div;
height = v_cur.item[5] / vdiv;
hmin = vmin = 0;
hmax = v_cur.item[1] - 1;
vmax = v_cur.item[5] - 1;
Expand All @@ -4149,8 +4183,9 @@ void video_cmd(char *cmd)
{
if (div >= 1 && div <= 4)
{
int vdiv = div * (v_cur.param.pr ? 2 : 1);
width = v_cur.item[1] / div;
height = v_cur.item[5] / div;
height = v_cur.item[5] / vdiv;
hmin = vmin = 0;
hmax = v_cur.item[1] - 1;
vmax = v_cur.item[5] - 1;
Expand Down
1 change: 1 addition & 0 deletions video.h
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,7 @@ void video_mode_adjust(bool force = false);
int hasAPI1_5();

void video_fb_enable(int enable, int n = 0);
void video_fb_reassert();
int video_fb_state();
void video_menu_bg(int n, int idle = 0);
int video_bg_has_picture();
Expand Down