From 80c6d052f2532ef49173fee61562d2cf7bcf7bd8 Mon Sep 17 00:00:00 2001
From: Romain Goyet <romain.goyet@numworks.com>
Date: Fri, 21 Jul 2017 14:02:12 +0200
Subject: [PATCH] [ion] Emscripten display uses an internal framebuffer

We operate on a framebuffer (push/pull rect), and then copy it all to
the screen at once. This avoids reading back from video memory. All in
all, it goes *much* faster this way.

Change-Id: I472d35988fde876906a9be71e0666b2c238114b3
---
 ion/src/emscripten/display.cpp | 49 +++++++++++++++++++++-------------
 ion/src/emscripten/display.h   |  1 +
 ion/src/emscripten/events.cpp  |  2 ++
 3 files changed, 33 insertions(+), 19 deletions(-)

diff --git a/ion/src/emscripten/display.cpp b/ion/src/emscripten/display.cpp
index 4fc647955..9406f2815 100644
--- a/ion/src/emscripten/display.cpp
+++ b/ion/src/emscripten/display.cpp
@@ -1,39 +1,30 @@
 #include "display.h"
+#include <kandinsky.h>
+
 extern "C" {
 #include <SDL/SDL.h>
 #include <assert.h>
+#include <stdlib.h>
+#include <emscripten.h>
 }
 
 SDL_Surface * screen = nullptr;
+static KDColor sPixels[Ion::Display::Width*Ion::Display::Height];
+static KDFrameBuffer sFrameBuffer = KDFrameBuffer(sPixels, KDSize(Ion::Display::Width, Ion::Display::Height));
 
 namespace Ion {
 namespace Display {
 
 void pushRect(KDRect r, const KDColor * pixels) {
-  if (SDL_MUSTLOCK(screen)) {
-    SDL_LockSurface(screen);
-  }
-  int pixelNumber = 0;
-  for (int j=r.top(); j<r.bottom(); j++) {
-    for (int i=r.left(); i<r.right(); i++) {
-      KDColor c = pixels[pixelNumber++];
-      *((Uint32*)screen->pixels + j * Ion::Display::Width + i) = SDL_MapRGB(screen->format, c.red(), c.green(), c.blue());
-    }
-  }
-  if (SDL_MUSTLOCK(screen)) {
-    SDL_UnlockSurface(screen);
-  }
-  SDL_UpdateRect(screen, r.x(), r.y(), r.width(), r.height());
+  sFrameBuffer.pushRect(r, pixels);
 }
 
 void pushRectUniform(KDRect r, KDColor c) {
-  Uint32 sdlColor = SDL_MapRGB(screen->format, c.red(), c.green(), c.blue());
-  SDL_Rect sdlRect = { r.x(), r.y(), r.width(), r.height() };
-  SDL_FillRect(screen, &sdlRect, sdlColor);
-  SDL_UpdateRect(screen, r.x(), r.y(), r.width(), r.height());
+  sFrameBuffer.pushRectUniform(r, c);
 }
 
 void pullRect(KDRect r, KDColor * pixels) {
+  sFrameBuffer.pullRect(r, pixels);
 }
 
 void waitForVBlank() {
@@ -48,7 +39,27 @@ namespace Emscripten {
 
 void init() {
   SDL_Init(SDL_INIT_VIDEO);
-  screen = SDL_SetVideoMode(Ion::Display::Width, Ion::Display::Height, 32, SDL_HWSURFACE);
+  screen = SDL_SetVideoMode(Ion::Display::Width, Ion::Display::Height, 32, SDL_SWSURFACE);
+  EM_ASM("SDL.defaults.copyOnLock = false; SDL.defaults.discardOnLock = true; SDL.defaults.opaqueFrontBuffer = false;");
+}
+
+void refresh() {
+  // Simply push the whole buffer to the surface
+  if (SDL_MUSTLOCK(screen)) {
+    SDL_LockSurface(screen);
+  }
+  int pixelNumber = 0;
+  for (int j=0; j<Ion::Display::Height; j++) {
+    for (int i=0; i<Ion::Display::Width; i++) {
+      KDColor c = sPixels[pixelNumber++];
+      *((Uint32*)screen->pixels + j * Ion::Display::Width + i) = SDL_MapRGB(screen->format, c.red(), c.green(), c.blue());
+    }
+  }
+
+  if (SDL_MUSTLOCK(screen)) {
+    SDL_UnlockSurface(screen);
+  }
+  SDL_UpdateRect(screen, 0, 0, Ion::Display::Width, Ion::Display::Height);
 }
 
 }
diff --git a/ion/src/emscripten/display.h b/ion/src/emscripten/display.h
index 0dcfa63ee..1d8094187 100644
--- a/ion/src/emscripten/display.h
+++ b/ion/src/emscripten/display.h
@@ -8,6 +8,7 @@ namespace Display {
 namespace Emscripten {
 
 void init();
+void refresh();
 
 }
 }
diff --git a/ion/src/emscripten/events.cpp b/ion/src/emscripten/events.cpp
index 65eb378b7..3b814b8ba 100644
--- a/ion/src/emscripten/events.cpp
+++ b/ion/src/emscripten/events.cpp
@@ -1,4 +1,5 @@
 #include <ion/events.h>
+#include "display.h"
 extern "C" {
 #include <SDL/SDL.h>
 }
@@ -28,6 +29,7 @@ static constexpr Event sEventForASCIICharAbove32[95] = {
 };
 
 Event getEvent(int * timeout) {
+  Ion::Display::Emscripten::refresh();
   if (sEvent != Ion::Events::None) {
     Ion::Events::Event event = sEvent;
     sEvent = Ion::Events::None;