[apps/code] Repare print() in micropython

Change-Id: I43c46748b15d83e071c7b7f1e8448384ce5ad77f

apps/code/Makefile

@@ -6,4 +6,7 @@ app_objs += $(addprefix apps/code/,\
   program.o\
 )
 
+tests += $(addprefix apps/code/test/,\
+  mpprint.cpp\
+)
 app_images += apps/code/code_icon.png

apps/code/executor_controller.cpp

@@ -25,21 +25,47 @@ mp_obj_t execute_from_str(const char *str) {
   }
 }
 
+/* mp_hal_stdout_tx_strn_cooked symbol required by micropython at printing
+ * needs to access information about where to print (depending on the strings
+ * printed before). This 'context' is provided by the global sCurrentView that
+ * points to the content view only within the drawRect method (as runPython is
+ * called within drawRect). */
+static const ExecutorController::ContentView * sCurrentView = nullptr;
+
 extern "C"
 void mp_hal_stdout_tx_strn_cooked(const char * str, size_t len) {
-  KDContext * ctx = KDIonContext::sharedContext();
-  ctx->drawString(str, KDPoint(0, 0));
+  assert(sCurrentView != nullptr);
+  sCurrentView->print(str);
 }
 
 ExecutorController::ContentView::ContentView(Program * program) :
   View(),
-  m_program(program)
+  m_program(program),
+  m_printLocation(KDPointZero)
 {
 }
 
 void ExecutorController::ContentView::drawRect(KDContext * ctx, KDRect rect) const {
-  ctx->fillRect(bounds(), KDColorWhite);
+  assert(ctx == KDIonContext::sharedContext());
+  clearScreen(ctx);
+
+  assert(sCurrentView == nullptr);
+  sCurrentView = this;
+
+  // Reinitialize the print location
+  m_printLocation = KDPointZero;
   runPython();
+
+  sCurrentView = nullptr;
+}
+
+void ExecutorController::ContentView::print(const char * str) const {
+  KDContext * ctx = KDIonContext::sharedContext();
+  m_printLocation = ctx->drawString(str, m_printLocation);
+  if (bounds().height() < m_printLocation.y()) {
+    clearScreen(ctx);
+    m_printLocation = KDPoint(m_printLocation.x(), 0);
+  }
 }
 
 void ExecutorController::ContentView::runPython() const {
@@ -60,6 +86,10 @@ void ExecutorController::ContentView::runPython() const {
   free(pythonHeap);
 }
 
+void ExecutorController::ContentView::clearScreen(KDContext * ctx) const {
+  ctx->fillRect(bounds(), KDColorWhite);
+}
+
 ExecutorController::ExecutorController(Program * program) :
   ViewController(nullptr),
   m_view(program)

apps/code/executor_controller.h

@@ -11,15 +11,18 @@ public:
   ExecutorController(Program * program);
   View * view() override;
   bool handleEvent(Ion::Events::Event event) override;
-private:
   class ContentView : public View {
   public:
     ContentView(Program * program);
     void drawRect(KDContext * ctx, KDRect rect) const override;
+    void print(const char * str) const;
   private:
     void runPython() const;
+    void clearScreen(KDContext * ctx) const;
     Program * m_program;
+    mutable KDPoint m_printLocation;
   };
+private:
   ContentView m_view;
 };
 

apps/code/test/mpprint.cpp

@@ -0,0 +1,6 @@
+#include <stdlib.h>
+
+extern "C"
+void mp_hal_stdout_tx_strn_cooked(const char * str, size_t len) {
+}
+

python/port/mpconfigport.h

@@ -72,8 +72,7 @@ typedef long mp_off_t;
 
 #define SEEK_CUR 1
 
-//#define MP_PLAT_PRINT_STRN(str, len) mp_hal_stdout_tx_strn_cooked(str, len)
-#define MP_PLAT_PRINT_STRN(str, len) ((void)0)
+#define MP_PLAT_PRINT_STRN(str, len) mp_hal_stdout_tx_strn_cooked(str, len)
 
 // extra built in names to add to the global namespace
 #define MICROPY_PORT_BUILTINS \