feat: add DisplayDriver methods for UTF-8 filtering and text ellipsis

- Add translateUTF8ToBlocks() method to convert UTF-8 characters to displayable blocks
- Add drawTextEllipsized() method for text truncation with ellipsis
- Apply UTF-8 filtering to node names, recent contacts, and message content
- Use ellipsized text rendering for recent contacts to prevent overflow
- Addresses PR feedback by moving text processing to DisplayDriver level

Author: michaelhart

examples/companion_radio/ui-new/UITask.cpp

@@ -90,6 +90,7 @@ class HomeScreen : public UIScreen {
   bool _shutdown_init;
   AdvertPath recent[UI_RECENT_LIST_SIZE];
 
+
   void renderBatteryIndicator(DisplayDriver& display, uint16_t batteryMilliVolts) {
     // Convert millivolts to percentage
     const int minMilliVolts = 3000; // Minimum voltage (e.g., 3.0V)
@@ -157,10 +158,12 @@ class HomeScreen : public UIScreen {
   int render(DisplayDriver& display) override {
     char tmp[80];
     // node name
-    display.setCursor(0, 0);
     display.setTextSize(1);
     display.setColor(DisplayDriver::GREEN);
-    display.print(_node_prefs->node_name);
+    char filtered_name[sizeof(_node_prefs->node_name)];
+    display.translateUTF8ToBlocks(filtered_name, _node_prefs->node_name, sizeof(filtered_name));
+    display.setCursor(0, 0);
+    display.print(filtered_name);
 
     // battery voltage
     renderBatteryIndicator(display, _task->getBattMilliVolts());
@@ -199,8 +202,6 @@ class HomeScreen : public UIScreen {
       for (int i = 0; i < UI_RECENT_LIST_SIZE; i++, y += 11) {
         auto a = &recent[i];
         if (a->name[0] == 0) continue;  // empty slot
-        display.setCursor(0, y);
-        display.print(a->name);
         int secs = _rtc->getCurrentTime() - a->recv_timestamp;
         if (secs < 60) {
           sprintf(tmp, "%ds", secs);
@@ -209,7 +210,14 @@ class HomeScreen : public UIScreen {
         } else {
           sprintf(tmp, "%dh", secs / (60*60));
         }
-        display.setCursor(display.width() - display.getTextWidth(tmp) - 1, y);
+        
+        int timestamp_width = display.getTextWidth(tmp);
+        int max_name_width = display.width() - timestamp_width - 1;
+        
+        char filtered_recent_name[sizeof(a->name)];
+        display.translateUTF8ToBlocks(filtered_recent_name, a->name, sizeof(filtered_recent_name));
+        display.drawTextEllipsized(0, y, max_name_width, filtered_recent_name);
+        display.setCursor(display.width() - timestamp_width - 1, y);
         display.print(tmp);
       }
     } else if (_page == HomePage::RADIO) {
@@ -427,11 +435,15 @@ class MsgPreviewScreen : public UIScreen {
 
     display.setCursor(0, 14);
     display.setColor(DisplayDriver::YELLOW);
-    display.print(p->origin);
+    char filtered_origin[sizeof(p->origin)];
+    display.translateUTF8ToBlocks(filtered_origin, p->origin, sizeof(filtered_origin));
+    display.print(filtered_origin);
 
     display.setCursor(0, 25);
     display.setColor(DisplayDriver::LIGHT);
-    display.printWordWrap(p->msg, display.width());
+    char filtered_msg[sizeof(p->msg)];
+    display.translateUTF8ToBlocks(filtered_msg, p->msg, sizeof(filtered_msg));
+    display.printWordWrap(filtered_msg, display.width());
 
 #if AUTO_OFF_MILLIS==0 // probably e-ink
     return 10000; // 10 s

src/helpers/ui/DisplayDriver.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <stdint.h>
+#include <string.h>
 
 class DisplayDriver {
   int _w, _h;
@@ -31,5 +32,60 @@ class DisplayDriver {
     setCursor(mid_x - w/2, y);
     print(str);
   }
+  
+  // convert UTF-8 characters to displayable block characters for compatibility
+  virtual void translateUTF8ToBlocks(char* dest, const char* src, size_t dest_size) {
+    size_t j = 0;
+    for (size_t i = 0; src[i] != 0 && j < dest_size - 1; i++) {
+      unsigned char c = (unsigned char)src[i];
+      if (c >= 32 && c <= 126) {
+        dest[j++] = c;  // ASCII printable
+      } else if (c >= 0x80) {
+        dest[j++] = '\xDB';  // CP437 full block █
+        while (src[i+1] && (src[i+1] & 0xC0) == 0x80) 
+          i++;  // skip UTF-8 continuation bytes
+      }
+    }
+    dest[j] = 0;
+  }
+  
+  // draw text with ellipsis if it exceeds max_width
+  virtual void drawTextEllipsized(int x, int y, int max_width, const char* str) {
+    char temp_str[256];  // reasonable buffer size
+    size_t len = strlen(str);
+    if (len >= sizeof(temp_str)) len = sizeof(temp_str) - 1;
+    memcpy(temp_str, str, len);
+    temp_str[len] = 0;
+    
+    if (getTextWidth(temp_str) <= max_width) {
+      setCursor(x, y);
+      print(temp_str);
+      return;
+    }
+    
+    // for variable-width fonts (GxEPD), add space after ellipsis
+    // for fixed-width fonts (OLED), keep tight spacing to save precious characters
+    const char* ellipsis;
+    // use a simple heuristic: if 'i' and 'l' have different widths, it's variable-width
+    int i_width = getTextWidth("i");
+    int l_width = getTextWidth("l");
+    if (i_width != l_width) {
+      ellipsis = "... ";  // variable-width fonts: add space
+    } else {
+      ellipsis = "...";   // fixed-width fonts: no space
+    }
+    
+    int ellipsis_width = getTextWidth(ellipsis);
+    int str_len = strlen(temp_str);
+    
+    while (str_len > 0 && getTextWidth(temp_str) > max_width - ellipsis_width) {
+      temp_str[--str_len] = 0;
+    }
+    strcat(temp_str, ellipsis);
+    
+    setCursor(x, y);
+    print(temp_str);
+  }
+  
   virtual void endFrame() = 0;
 };