Display & UI Modules

SyntropicOS provides hardware-independent framebuffer drawing (syn_canvas), 2D graphics primitives (syn_gfx), and a zero-allocation immediate-mode GUI engine (syn_imgui).

---

1. Framebuffer Display Canvas (display/syn_canvas.h)

The syn_canvas driver provides a hardware-agnostic framebuffer supporting both 1bpp (Monochrome OLED) and 16bpp (RGB565 TFT) displays.

Architecture Data Flow

flowchart LR
    Drawing["Drawing Primitives (line, text, rect)"] --> Canvas["SYN_Canvas Framebuffer"]
    Canvas -->|syn_canvas_flush| HardwareFn["Flush Function (SPI/I2C DMA)"]
    HardwareFn --> OLED["Physical OLED / TFT Display"]

Complete Code Example (SSD1306 Mono OLED)

#include <syntropic/display/syn_canvas.h>

// Monochrome OLED (128×64 pixels, 1bpp = 1024 bytes)
static uint8_t framebuf[128 * 64 / 8];
static SYN_Canvas canvas;

// Flush callback: sends raw framebuffer bytes to display driver over I2C/SPI
static void oled_flush_callback(const uint8_t *buf, size_t len, void *ctx) {
    // Send 1024-byte framebuffer via I2C/SPI DMA
    SSD1306_Transmit_Buffer(buf, len);
}

void display_setup(void) {
    // Initialize canvas: 128px width, 64px height, 1bpp monochrome format
    syn_canvas_init(&canvas, framebuf, 128, 64, 1, oled_flush_callback, NULL);
}

void render_dashboard(int temperature, int battery_pct) {
    char str[32];

    // Clear previous frame
    syn_canvas_clear(&canvas);

    // Draw header text using built-in 5x7 font
    syn_canvas_text(&canvas, 0, 0, "SyntropicOS Dashboard");

    // Draw horizontal dividing line
    syn_canvas_line(&canvas, 0, 10, 127, 10);

    // Draw metric labels
    snprintf(str, sizeof(str), "Temp: %d C", temperature);
    syn_canvas_text(&canvas, 0, 20, str);

    snprintf(str, sizeof(str), "Batt: %d%%", battery_pct);
    syn_canvas_text(&canvas, 0, 32, str);

    // Draw battery level progress bar outline & fill
    syn_canvas_rect(&canvas, 70, 32, 50, 8); // Outline
    syn_canvas_fill_rect(&canvas, 71, 33, (battery_pct * 48) / 100, 6); // Fill

    // Push framebuffer to hardware
    syn_canvas_flush(&canvas);
}

---

2. Immediate-Mode GUI (ui/syn_imgui.h)

The syn_imgui module provides a zero-allocation Immediate-Mode GUI framework. Widgets are drawn and input-tested in a single pass each frame without maintaining complex DOM trees or allocating dynamic heap memory.

Features

• Widgets: Buttons, Sliders, Checkboxes, Progress Bars, Gauges, Real-time Graphs.
• Navigation: Rotary Encoder step navigation, Button clicks, or Touchscreen X/Y coordinates.

Complete IMGUI Menu Example

#include <syntropic/ui/syn_imgui.h>

static SYN_IMGUI ui;
static bool heater_enabled = false;
static int target_temp = 25;

void render_gui(void) {
    syn_imgui_begin_frame(&ui);

    syn_imgui_label(&ui, 10, 5, "Temperature Control");

    // Interactive Checkbox widget
    if (syn_imgui_checkbox(&ui, 10, 20, "Enable Heater", &heater_enabled)) {
        // Toggle callback logic
    }

    // Interactive Slider widget
    if (heater_enabled) {
        syn_imgui_slider(&ui, 10, 40, 100, 10, "Set Temp", &target_temp, 15, 40);
    }

    syn_imgui_end_frame(&ui);
}

Advanced UI Widgets

Virtual PIN Keypad (syn_imgui_numpad)

Renders a 4x3 keypad grid (1-9, 0, C Clear, OK Confirm) supporting touch taps and rotary encoder navigation.

static char pin_code[8] = "";

void render_pin_screen(SYN_IMGUI_Context *ctx) {
    // Render 4x3 PIN entry numpad with '*' digit masking
    int status = syn_imgui_numpad(ctx, pin_code, sizeof(pin_code), true, 0, 0, 120, 60);

    if (status == 1) {
        // OK pressed: validate passcode
        if (strcmp(pin_code, "1234") == 0) {
            syn_imgui_toast(ctx, "Access Granted", 2000, current_ms, start_ms);
        } else {
            syn_imgui_toast(ctx, "Invalid PIN", 2000, current_ms, start_ms);
            pin_code[0] = '\0'; // reset
        }
    } else if (status == -1) {
        // Clear/Back pressed on empty buffer: exit screen
        navigate_back();
    }
}

Transient Toast Banner (syn_imgui_toast)

Renders a floating notification overlay banner at the top of the display that auto-dismisses after duration_ms.

// Displays a 2-second status notification overlay
syn_imgui_toast(ctx, "Settings Saved!", 2000, current_tick_ms, toast_start_ms);

---

3. Character LCD & OLED Direct Drivers (display/syn_charlcd.h & display/syn_oled.h)

Supports HD44780 16x2 / 20x4 Character LCD displays (GPIO 4-bit / I2C backpack) and SSD1306 / SH1106 monochrome OLED direct command initialization.

#include <syntropic/display/syn_charlcd.h>
#include <syntropic/display/syn_oled.h>

void charlcd_demo(void) {
    syn_charlcd_init(16, 2);
    syn_charlcd_set_cursor(0, 0);
    syn_charlcd_print("SyntropicOS v2.0");
}

---

4. 7-Segment LED Multiplex Driver (display/syn_seg7.h)

Multiplexed 7-segment digital display driver supporting decimal integers, floating-point rendering, and custom hexadecimal patterns.

#include <syntropic/display/syn_seg7.h>

void seg7_demo(void) {
    // Render float number 12.34 across 4 digits
    syn_seg7_display_float(12.34f, 2);
}