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fix: improve oscilloscope auto-scaling and data handling #70

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Merged
hsb689 merged 1 commit into from
Mar 3, 2026
Merged

fix: improve oscilloscope auto-scaling and data handling #70

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65 changes: 42 additions & 23 deletions source/widgets/scope/sgl_scope.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@
*/

#include <stdio.h>
#include <limits.h>
#include <sgl_theme.h>
#include "sgl_scope.h"

Expand Down Expand Up @@ -203,25 +204,46 @@ static void scope_construct_cb(sgl_surf_t *surf, sgl_obj_t* obj, sgl_event_t *ev
sgl_draw_rect(surf, &obj->area, &obj->coords, &bg_rect);

// Compute waveform display parameters
uint16_t display_min = scope->min_value;
uint16_t display_max = scope->max_value;
int16_t display_min = scope->min_value;
int16_t display_max = scope->max_value;
int16_t actual_min = display_min; // Actual min/max of waveform data (for labels)
int16_t actual_max = display_max; // Actual max of waveform data (for labels)

// If auto-scaling is enabled, use runtime min/max values
// If auto-scaling is enabled, recalculate min/max from current buffer data
if (scope->auto_scale) {
display_min = scope->running_min;
display_max = scope->running_max;
// Recalculate running_min and running_max based on current data in buffer
if (scope->display_count > 0) {
display_min = scope->data_buffer[0];
display_max = scope->data_buffer[0];

// Iterate through all data points in buffer to find min/max
uint32_t end_index = (scope->display_count < scope->data_len) ? scope->display_count : scope->data_len;
for (uint32_t i = 0; i < end_index; i++) {
int16_t val = scope->data_buffer[i];
if (val < display_min) display_min = val;
if (val > display_max) display_max = val;
}

// Save actual data min/max for label display
actual_min = display_min;
actual_max = display_max;

// Update running values for next frame
scope->running_min = display_min;
scope->running_max = display_max;
}

// Add margin to prevent waveform from touching borders
uint16_t margin = (display_max - display_min) / 10;
int32_t margin = (int32_t)(display_max - display_min) / 10;
if (margin == 0) margin = 1;

display_min = (display_min > margin) ? display_min - margin : 0;
display_max = (display_max + margin < 0xFFFF) ? display_max + margin : 0xFFFF;
display_min = (display_min > INT16_MIN + margin) ? display_min - margin : INT16_MIN;
display_max = (display_max < INT16_MAX - margin) ? display_max + margin : INT16_MAX;
}

// Avoid division by zero if min equals max
if (display_min == display_max) {
if (display_max < 0xFFFF) {
if (display_max < INT16_MAX) {
display_max++;
} else {
display_min--;
Expand Down Expand Up @@ -330,18 +352,19 @@ static void scope_construct_cb(sgl_surf_t *surf, sgl_obj_t* obj, sgl_event_t *ev

sgl_area_selfclip(&text_area, &obj->area);

// Display maximum value
sprintf(label_text, "%u", display_max);
// Display actual maximum value of waveform data
sprintf(label_text, "%d", actual_max);
sgl_draw_string(surf, &text_area, obj->coords.x1 + 2, obj->coords.y1 + 2,
label_text, scope->y_label_color, scope->alpha, scope->y_label_font);

// Display minimum value
sprintf(label_text, "%u", display_min);
// Display actual minimum value of waveform data
sprintf(label_text, "%d", actual_min);
sgl_draw_string(surf, &text_area, obj->coords.x1 + 2, obj->coords.y2 - scope->y_label_font->font_height - 2,
label_text, scope->y_label_color, scope->alpha, scope->y_label_font);

// Display mid-range value
uint16_t mid_value = (display_max + display_min) / 2;
// Display mid-range value of actual waveform
int16_t mid_value = (actual_max + actual_min) / 2;
sprintf(label_text, "%d", mid_value);
sprintf(label_text, "%u", mid_value);
sgl_draw_string(surf, &text_area, obj->coords.x1 + 2, y_center - scope->y_label_font->font_height/2,
label_text, scope->y_label_color, scope->alpha, scope->y_label_font);
Expand Down Expand Up @@ -373,8 +396,8 @@ sgl_obj_t* sgl_scope_create(sgl_obj_t* parent)
scope->border_color = sgl_rgb(150, 150, 150); // Light gray outer border
scope->min_value = 0;
scope->max_value = 0xFFFF;
scope->running_min = 0xFFFF; // Initialize runtime minimum
scope->running_max = 0; // Initialize runtime maximum
scope->running_min = INT16_MAX; // Initialize runtime minimum to max int16_t value
scope->running_max = INT16_MIN; // Initialize runtime maximum to min int16_t value
scope->auto_scale = 1; // Enable auto-scaling by default
scope->line_width = 2; // Default line thickness
scope->max_display_points = 0; // Display all points by default
Expand All @@ -400,12 +423,8 @@ void sgl_scope_append_data(sgl_obj_t* obj, int16_t value)
{
sgl_scope_t *scope = (sgl_scope_t*)obj;

// update the auto scale only if the auto_scale is enabled
if (scope->auto_scale) {
if (value < scope->running_min) scope->running_min = value;
if (value > scope->running_max) scope->running_max = value;
}

// Simply append the data point to the buffer
// Min/max will be recalculated during drawing if auto-scale is enabled
scope->data_buffer[scope->current_index] = value;

if (sgl_is_pow2(scope->data_len)) {
Expand Down
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