RPi Pico port compilation (#174)

* use ESP_PLATFORM conditionals around ESP32-specific bits

* use LIST(APPEND LV_SRC ...)

* handle LV_PNG_PP_OPTIONS for non-ESP platform

* Set LV_BINDINGS_DIR not relative to MICROPY_DIR (for out-of-tree builds)

* add cmake file for use with USER_C_MODULE=bindings.cmake

* interface lib for lvgl

Related PRs: 
- lvgl/lv_micropython#42
- lvgl/lvgl#2532

Author: eudoxos

bindings.cmake

@@ -0,0 +1,19 @@
+# This file is to be given as "make USER_C_MODULES=..." when building Micropython port
+
+include(${CMAKE_CURRENT_LIST_DIR}/mkrules.cmake)
+
+# create targets for generated files
+all_lv_bindings()
+
+# lvgl bindings target (the mpy module)
+add_library(usermod_lv_bindings INTERFACE)
+target_sources(usermod_lv_bindings INTERFACE ${LV_SRC})
+target_include_directories(usermod_lv_bindings INTERFACE ${LV_INCLUDE})
+
+# lvgl bindings depend on lvgl itself, pull it in
+include(${LVGL_DIR}/CMakeLists.txt)
+target_link_libraries(usermod_lv_bindings INTERFACE lvgl_interface)
+
+# make usermod (target declared by Micropython for all user compiled modules) link to bindings
+# this way the bindings (and transitively lvgl_interface) get proper compilation flags
+target_link_libraries(usermod INTERFACE usermod_lv_bindings)

mkrules.cmake

@@ -2,7 +2,7 @@
 find_package(Python3 REQUIRED COMPONENTS Interpreter)
 find_program(AWK awk mawk gawk)
 
-set(LV_BINDINGS_DIR ${MICROPY_DIR}/lib/lv_bindings)
+set(LV_BINDINGS_DIR ${CMAKE_CURRENT_LIST_DIR})
 
 # Common function for creating LV bindings
 
@@ -81,7 +81,9 @@ set(LV_PNG_DIR ${LV_BINDINGS_DIR}/driver/png/lodepng)
 set(LV_MP ${CMAKE_BINARY_DIR}/lv_mp.c)
 set(LV_PNG ${CMAKE_BINARY_DIR}/lv_png.c)
 set(LV_PNG_C ${CMAKE_BINARY_DIR}/lv_png_c.c)
-set(LV_ESPIDF ${CMAKE_BINARY_DIR}/lv_espidf.c)
+if(ESP_PLATFORM)
+    set(LV_ESPIDF ${CMAKE_BINARY_DIR}/lv_espidf.c)
+endif()
 
 # Function for creating all specific bindings
 
@@ -105,7 +107,11 @@ function(all_lv_bindings)
 
     file(GLOB_RECURSE LV_PNG_HEADERS ${LV_PNG_DIR}/*.h)
     configure_file(${LV_PNG_DIR}/lodepng.cpp ${LV_PNG_C} COPYONLY)
-    idf_build_set_property(COMPILE_DEFINITIONS "${LV_PNG_PP_OPTIONS}" APPEND)
+    if(ESP_PLATFORM)
+        idf_build_set_property(COMPILE_DEFINITIONS "${LV_PNG_PP_OPTIONS}" APPEND)
+    else()
+        add_definitions(${LV_PNG_PP_OPTIONS})
+    endif()
     lv_bindings(
         OUTPUT
             ${LV_PNG}
@@ -120,30 +126,31 @@ function(all_lv_bindings)
     )
 
     # ESPIDF bindings
-
-    file(GLOB_RECURSE LV_ESPIDF_HEADERS ${IDF_PATH}/components/*.h ${LV_BINDINGS_DIR}/driver/esp32/*.h)
-    lv_bindings(
-        OUTPUT
-            ${LV_ESPIDF}
-        INPUT
-            ${LV_BINDINGS_DIR}/driver/esp32/espidf.h
-        DEPENDS
-            ${LV_ESPIDF_HEADERS}
-        PP_OPTIONS
-            -DPYCPARSER
-        GEN_OPTIONS
-             -M espidf
-        FILTER
-            i2s_ll.h
-            i2s_hal.h
-            esp_intr_alloc.h
-            soc/spi_periph.h
-            rom/ets_sys.h
-            soc/sens_struct.h
-            soc/rtc.h
-            driver/periph_ctrl.h
-            include/esp_private
-    )
+    if(ESP_PLATFORM)
+        file(GLOB_RECURSE LV_ESPIDF_HEADERS ${IDF_PATH}/components/*.h ${LV_BINDINGS_DIR}/driver/esp32/*.h)
+        lv_bindings(
+            OUTPUT
+                ${LV_ESPIDF}
+            INPUT
+                ${LV_BINDINGS_DIR}/driver/esp32/espidf.h
+            DEPENDS
+                ${LV_ESPIDF_HEADERS}
+            PP_OPTIONS
+                -DPYCPARSER
+            GEN_OPTIONS
+                 -M espidf
+            FILTER
+                i2s_ll.h
+                i2s_hal.h
+                esp_intr_alloc.h
+                soc/spi_periph.h
+                rom/ets_sys.h
+                soc/sens_struct.h
+                soc/rtc.h
+                driver/periph_ctrl.h
+                include/esp_private
+        )
+    endif(ESP_PLATFORM)
 
 endfunction()
 
@@ -158,16 +165,16 @@ set(LV_INCLUDE
 
 set(LV_SRC
     ${LV_MP}
-
-    ${LV_BINDINGS_DIR}/driver/esp32/espidf.c
-    ${LV_BINDINGS_DIR}/driver/esp32/modrtch.c
-    ${LV_BINDINGS_DIR}/driver/esp32/sh2lib.c
-
     ${LV_PNG}
     ${LV_PNG_C}
     ${LV_BINDINGS_DIR}/driver/png/mp_lodepng.c
-
-    ${LV_ESPIDF}
 )
 
-
+if(ESP_PLATFORM)
+    LIST(APPEND LV_SRC
+        ${LV_BINDINGS_DIR}/driver/esp32/espidf.c
+        ${LV_BINDINGS_DIR}/driver/esp32/modrtch.c
+        ${LV_BINDINGS_DIR}/driver/esp32/sh2lib.c
+        ${LV_ESPIDF}
+    )
+endif(ESP_PLATFORM)