Prevent Lua from allocating all heap memory (Horus) (#4440)

* Fixes #4284: Prevent Lua from allocating all heap memory (Horus)
Lua bitmap functions cleanup and docs update
Added x or y < 0 check to drawBitmap()

* Proper float constant

radio/src/lua/api_lcd.cpp

@@ -325,10 +325,19 @@ static int luaLcdDrawSource(lua_State *L)
 /*luadoc
 @function Bitmap.open(name)
 
-Loads a bitmap in memory, for later use with lcd.drawBitmap()
+Loads a bitmap in memory, for later use with lcd.drawBitmap(). Bitmaps should be loaded only
+once, returned object should be stored and used for drawing. If loading fails for whatever
+reason the resulting bitmap object will have width and height set to zero.
+
+Bitmap loading can fail if:
+ * File is not found or contains invalid image
+ * System is low on memory
+ * Combined memory usage of all Lua script bitmaps exceeds certain value
 
 @param name (string) full path to the bitmap on SD card (i.e. “/IMAGES/test.bmp”)
 
+@retval bitmap (object) a bitmap object that can be used with other bitmap functions
+
 @notice Only available on Horus
 
 @status current Introduced in 2.2.0
@@ -337,18 +346,25 @@ static int luaOpenBitmap(lua_State * L)
 {
   const char * filename = luaL_checkstring(L, 1);
 
-  BitmapBuffer ** ptr = (BitmapBuffer **)lua_newuserdata(L, sizeof(BitmapBuffer *));
-  *ptr = BitmapBuffer::load(filename);
+  BitmapBuffer ** b = (BitmapBuffer **)lua_newuserdata(L, sizeof(BitmapBuffer *));
 
-  if (*ptr == NULL && G(L)->gcrunning) {
-    luaC_fullgc(L, 1);  /* try to free some memory... */
-    *ptr = BitmapBuffer::load(filename);  /* try again */
+  if (luaExtraMemoryUsage > LUA_MEM_EXTRA_MAX) {
+    // already allocated more than max allowed, fail
+    TRACE("luaOpenBitmap: Error, using too much memory %u/%u", luaExtraMemoryUsage, LUA_MEM_EXTRA_MAX);
+    *b = 0;
+  }
+  else {
+    *b = BitmapBuffer::load(filename);
+    if (*b == NULL && G(L)->gcrunning) {
+      luaC_fullgc(L, 1);  /* try to free some memory... */
+      *b = BitmapBuffer::load(filename);  /* try again */
+    }
   }
 
-  if (*ptr) {
-    uint32_t size = (*ptr)->getDataSize();
+  if (*b) {
+    uint32_t size = (*b)->getDataSize();
     luaExtraMemoryUsage += size;
-    TRACE("luaOpenBitmap: %p (%u)", *ptr, size);
+    TRACE("luaOpenBitmap: %p (%u)", *b, size);
   }
 
   luaL_getmetatable(L, LUA_BITMAPHANDLE);
@@ -364,13 +380,16 @@ static BitmapBuffer * checkBitmap(lua_State * L, int index)
   return *b;
 }
 
-
 /*luadoc
 @function Bitmap.getSize(name)
 
-Return width, heigh of a bitmap in memory
+Return width, height of a bitmap object
 
-@param bitmap (pointer) point to a bitmap previously opened with Bipmap.open()
+@param bitmap (pointer) point to a bitmap previously opened with Bitmap.open()
+
+@retval multiple returns 2 values:
+ * (number) width in pixels
+ * (number) height in pixels
 
 @notice Only available on Horus
 
@@ -378,7 +397,7 @@ Return width, heigh of a bitmap in memory
 */
 static int luaGetBitmapSize(lua_State * L)
 {
-  BitmapBuffer * b = checkBitmap(L, 1);
+  const BitmapBuffer * b = checkBitmap(L, 1);
   if (b) {
     lua_pushinteger(L, b->getWidth());
     lua_pushinteger(L, b->getHeight());
@@ -392,11 +411,18 @@ static int luaGetBitmapSize(lua_State * L)
 
 static int luaDestroyBitmap(lua_State * L)
 {
-  BitmapBuffer * ptr = checkBitmap(L, 1);
-  uint32_t size = ptr->getDataSize();
-  TRACE("luaDestroyBitmap: %p (%u)", ptr, size);
-  if (luaExtraMemoryUsage > size) luaExtraMemoryUsage -= size;
-  delete ptr;
+  BitmapBuffer * b = checkBitmap(L, 1);
+  if (b) {
+    uint32_t size = b->getDataSize();
+    TRACE("luaDestroyBitmap: %p (%u)", b, size);
+    if (luaExtraMemoryUsage >= size) {
+      luaExtraMemoryUsage -= size;
+    }
+    else {
+      luaExtraMemoryUsage = 0;
+    }
+    delete b;
+  }
   return 0;
 }
 
@@ -421,11 +447,12 @@ void registerBitmapClass(lua_State * L)
 
 Displays a bitmap at (x,y)
 
-@param bitmap (pointer) point to a bitmap previously opened with Bipmap.open()
+@param bitmap (pointer) point to a bitmap previously opened with Bitmap.open()
 
 @param x,y (positive numbers) starting coordinates
 
-@param scale (positive numbers) scale in %, 50 divides size by two, 100 is unchanged, 200 doubles size
+@param scale (positive numbers) scale in %, 50 divides size by two, 100 is unchanged, 200 doubles size.
+Omitting scale draws image in 1:1 scale and is faster than specifying 100 for scale.
 
 @notice Only available on Horus
 
@@ -434,15 +461,19 @@ Displays a bitmap at (x,y)
 static int luaLcdDrawBitmap(lua_State *L)
 {
   if (!luaLcdAllowed) return 0;
-  const BitmapBuffer * bitmap = checkBitmap(L, 1);
-  int x = luaL_checkinteger(L, 2);
-  int y = luaL_checkinteger(L, 3);
-  unsigned scale = luaL_optunsigned(L, 4, 0);
+  const BitmapBuffer * b = checkBitmap(L, 1);
 
-  if (bitmap) {
-    lcd->drawBitmap(x, y, bitmap, 0, 0, 0, 0, (float) scale/100);
+  if (b) {
+    unsigned int x = luaL_checkunsigned(L, 2);
+    unsigned int y = luaL_checkunsigned(L, 3);
+    unsigned int scale = luaL_optunsigned(L, 4, 0);
+    if (scale) {
+      lcd->drawBitmap(x, y, b, 0, 0, 0, 0, scale/100.0f);
+    }
+    else {
+      lcd->drawBitmap(x, y, b);
+    }
   }
-
   return 0;
 }
 #elif LCD_DEPTH > 1