separate display to its own file

display.cpp

@@ -0,0 +1,86 @@
+#include <ctype.h>
+#include <cstring>
+
+#include "hardware/i2c.h"
+#include "pico-ssd1306/ssd1306.h"
+#include "pico-ssd1306/textRenderer/TextRenderer.h"
+#include "hardware/gpio.h"
+
+#include "display.h"
+#include <new>
+
+
+using namespace pico_ssd1306;
+
+// Implement the methods declared in `display.h`.
+
+// Use in-place storage for the SSD1306 object to avoid heap allocation on
+// constrained embedded systems. The storage is sized using the complete
+// `SSD1306` type (this file includes the concrete header), and the object
+// is constructed with placement-new during `init()` and explicitly destroyed
+// in the destructor.
+namespace {
+    alignas(SSD1306) unsigned char display_storage[sizeof(SSD1306)];
+    bool display_constructed = false;
+}
+DisplayManager::DisplayManager()
+    : display_(nullptr)
+{
+    last_echo_[0] = '\0';
+}
+
+DisplayManager::~DisplayManager() {
+    if (display_constructed && display_) {
+        // Call destructor explicitly since we used placement-new.
+        display_->~SSD1306();
+        display_constructed = false;
+    }
+    display_ = nullptr;
+}
+
+// (No singleton accessor — the DisplayManager is constructed explicitly by callers.)
+
+void DisplayManager::init(uint8_t i2c_addr) {
+    if (display_) return; // already initialized
+
+    // Initialize I2C for the SSD1306 display (common pins: SDA=GPIO4, SCL=GPIO5)
+    i2c_init(i2c0, 400 * 1000);
+    gpio_set_function(4, GPIO_FUNC_I2C);
+    gpio_set_function(5, GPIO_FUNC_I2C);
+    gpio_pull_up(4);
+    gpio_pull_up(5);
+
+    // Construct the display object in pre-allocated storage to avoid heap use.
+    display_ = reinterpret_cast<SSD1306 *>(display_storage);
+    new (display_) SSD1306(i2c0, i2c_addr, Size::W128xH64);
+    display_constructed = true;
+    display_->setOrientation(false);
+    display_->clear();
+    display_->sendBuffer();
+
+    last_echo_[0] = '\0';
+    refresh("> ", nullptr);
+}
+
+void DisplayManager::refresh(const char *current_input, const char *last_echo) {
+    if (!display_) return;
+    display_->clear();
+
+    size_t input_len = current_input ? strlen(current_input) : 0;
+    const unsigned char *input_font = (input_len > LAST_ECHO_VISIBLE_CHARS) ? font_5x8 : font_12x16;
+
+    pico_ssd1306::drawText(display_, input_font, current_input ? current_input : "", 0, 0);
+
+    const char *echo_to_draw = last_echo ? last_echo : (last_echo_[0] ? last_echo_ : "");
+    pico_ssd1306::drawText(display_, font_12x16, echo_to_draw, 0, 20);
+
+    display_->sendBuffer();
+}
+
+void DisplayManager::set_last_echo(const char *text) {
+    if (!text) return;
+    strncpy(last_echo_, text, sizeof(last_echo_) - 1);
+    last_echo_[sizeof(last_echo_) - 1] = '\0';
+}
+
+// No C-compatible wrappers: prefer `DisplayManager::instance()` API directly.