sim: embedd background bmp and load from memory

Loading the file from disk introduces a slight dependency on the working
directory for the simulator. Prevent that by loading the bmp from
memory.

Use a python script to convert the backround bmp image to a C header
file. Include this header in `main.cpp` and load the bmp from memory.

CMakeLists.txt

@@ -325,6 +325,10 @@ endif()
 
 target_include_directories(infinisim PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}/gif-h")
 
+# embedd background image for the status window to use
+add_subdirectory(img)
+add_dependencies(infinisim infinisim_img_background)
+
 install(TARGETS infinisim DESTINATION bin)
 
 # helper library to manipulate littlefs raw image

img/CMakeLists.txt

@@ -0,0 +1,26 @@
+message(STATUS "folder img: converting background.bmp to C file to include in binary")
+
+if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12)
+   # FindPython3 module introduces with CMake 3.12
+   # https://cmake.org/cmake/help/latest/module/FindPython3.html
+   find_package(Python3 REQUIRED)
+else()
+   set(Python3_EXECUTABLE "python")
+endif()
+
+set(bmp_file ${CMAKE_CURRENT_SOURCE_DIR}/sim_background.bmp)
+set(out_file ${CMAKE_CURRENT_BINARY_DIR}/sim_background.h)
+# call python script to convert image to c file
+add_custom_command(
+   OUTPUT ${out_file}
+   COMMAND "${Python3_EXECUTABLE}" ${CMAKE_CURRENT_SOURCE_DIR}/convert_bmp_to_header.py
+   ${bmp_file}
+   --var-name "SIM_BACKGROUND"
+   --output ${out_file}
+   DEPENDS ${bmp_file}
+   WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+)
+# add target that can be added as dependency to infinisim target to trigger creation of C-file
+add_custom_target(infinisim_img_background
+   DEPENDS ${out_file}
+)

img/convert_bmp_to_header.py

@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+import argparse
+
+parser = argparse.ArgumentParser()
+
+parser.add_argument("bmp",
+    help="Path to bmp to convert to C header file")
+parser.add_argument("--var-name",
+   help="name of the variable to make the bmp data available",
+   default="IMAGE_DATA")
+parser.add_argument("-o", "--output",
+   help="Path where to create C header file",
+   required=True)
+args = parser.parse_args()
+
+with open(args.output, "w", encoding="utf-8") as f:
+    # conversion script based on:
+    # https://stackoverflow.com/questions/18422123/sdl-embed-image-inside-program-executable
+    f.write("static const unsigned char {:s}[] = {{{:s}}};".format(
+        args.var_name,
+        ",".join(str(b) for b in open(args.bmp, "rb").read())))

main.cpp

@@ -69,6 +69,8 @@
 #endif
 #include <gif.h>
 
+#include "img/sim_background.h" // provides variable SIM_BACKGROUND
+
 /*********************
  *      DEFINES
  *********************/
@@ -426,8 +428,10 @@ public:
         init_NRF_WDT();
         init_NRF_POWER();
 
-        // Attempt to load background PNG for the status display window
+        // Attempt to load background BMP from memory for the status display window
-        SDL_Surface* simDisplayBgRaw = SDL_LoadBMP("img/sim_background.bmp");
+        const size_t SIM_BACKGROUND_size = sizeof(SIM_BACKGROUND);
+        SDL_RWops *rw = SDL_RWFromMem((void*)SIM_BACKGROUND, SIM_BACKGROUND_size);
+        SDL_Surface* simDisplayBgRaw = SDL_LoadBMP_RW(rw, 1);
         if (simDisplayBgRaw == NULL) {
           printf("Failed to load sim background image: %s\n", SDL_GetError());
         } else {