base: Redesign internal frame buffer handling

Currently, frame buffer handling in gem5 is quite ad hoc. In practice,
we pass around naked pointers to raw pixel data and expect consumers
to convert frame buffers using the (broken) VideoConverter.

This changeset completely redesigns the way we handle frame buffers
internally. In summary, it fixes several color conversion bugs, adds
support for more color formats (e.g., big endian), and makes the code
base easier to follow.

In the new world, gem5 always represents pixel data using the Pixel
struct when pixels need to be passed between different classes (e.g.,
a display controller and the VNC server). Producers of entire frames
(e.g., display controllers) should use the FrameBuffer class to
represent a frame.

Frame producers are expected to create one instance of the FrameBuffer
class in their constructors and register it with its consumers
once. Consumers are expected to check the dimensions of the frame
buffer when they consume it.

Conversion between the external representation and the internal
representation is supported for all common "true color" RGB formats of
up to 32-bit color depth. The external pixel representation is
expected to be between 1 and 4 bytes in either big endian or little
endian. Color channels are assumed to be contiguous ranges of bits
within each pixel word. The external pixel value is scaled to an 8-bit
internal representation using a floating multiplication to map it to
the entire 8-bit range.

1 files changed, 49 insertions, 35 deletions

diff --git a/src/base/vnc/vncserver.cc b/src/base/vnc/vncserver.cc
index 6dc2f2f10..20f3bc8fe 100644
--- a/src/base/vnc/vncserver.cc
+++ b/src/base/vnc/vncserver.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010 ARM Limited
+ * Copyright (c) 2010, 2015 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -61,6 +61,7 @@
 
 #include <cerrno>
 #include <cstdio>
+#include <cstddef>
 
 #include "base/atomicio.hh"
 #include "base/bitmap.hh"
@@ -74,6 +75,12 @@
 
 using namespace std;
 
+const PixelConverter VncServer::pixelConverter(
+    4,        // 4 bytes / pixel
+    16, 8, 0, // R in [23, 16], G in [15, 8], B in [7, 0]
+    8, 8, 8,  // 8 bits / channel
+    LittleEndianByteOrder);
+
 /** @file
  * Implementiation of a VNC server
  */
@@ -122,20 +129,19 @@ VncServer::VncServer(const Params *p)
 
     curState = WaitForProtocolVersion;
 
-    // currently we only support this one pixel format
-    // unpacked 32bit rgb (rgb888 + 8 bits of nothing/alpha)
-    // keep it around for telling the client and making
-    // sure the client cooperates
-    pixelFormat.bpp = 32;
-    pixelFormat.depth = 24;
-    pixelFormat.bigendian = 0;
+    // We currently only support one pixel format. Extract the pixel
+    // representation from our PixelConverter instance and keep it
+    // around for telling the client and making sure it cooperates
+    pixelFormat.bpp = 8 * pixelConverter.length;
+    pixelFormat.depth = pixelConverter.depth;
+    pixelFormat.bigendian = pixelConverter.byte_order == BigEndianByteOrder;
     pixelFormat.truecolor = 1;
-    pixelFormat.redmax = 0xff;
-    pixelFormat.greenmax = 0xff;
-    pixelFormat.bluemax = 0xff;
-    pixelFormat.redshift = 16;
-    pixelFormat.greenshift = 8;
-    pixelFormat.blueshift = 0;
+    pixelFormat.redmax = pixelConverter.ch_r.mask;
+    pixelFormat.greenmax = pixelConverter.ch_g.mask;
+    pixelFormat.bluemax = pixelConverter.ch_b.mask;
+    pixelFormat.redshift = pixelConverter.ch_r.offset;
+    pixelFormat.greenshift = pixelConverter.ch_g.offset;
+    pixelFormat.blueshift = pixelConverter.ch_b.offset;
 
     DPRINTF(VNC, "Vnc server created at port %d\n", p->port);
 }
@@ -615,13 +621,11 @@ void
 VncServer::sendFrameBufferUpdate()
 {
 
-    if (!fbPtr || dataFd <= 0 || curState != NormalPhase || !sendUpdate) {
+    if (dataFd <= 0 || curState != NormalPhase || !sendUpdate) {
         DPRINTF(VNC, "NOT sending framebuffer update\n");
         return;
     }
 
-    assert(vc);
-
     // The client will request data constantly, unless we throttle it
     sendUpdate = false;
 
@@ -650,19 +654,25 @@ VncServer::sendFrameBufferUpdate()
     write(&fbu);
     write(&fbr);
 
-    assert(fbPtr);
+    assert(fb);
 
-    uint8_t *tmp = vc->convert(fbPtr);
-    uint64_t num_pixels = videoWidth() * videoHeight();
-    write(tmp, num_pixels * sizeof(uint32_t));
-    delete [] tmp;
+    std::vector<uint8_t> line_buffer(pixelConverter.length * fb->width());
+    for (int y = 0; y < fb->height(); ++y) {
+        // Convert and send a line at a time
+        uint8_t *raw_pixel(line_buffer.data());
+        for (unsigned x = 0; x < fb->width(); ++x) {
+            pixelConverter.fromPixel(raw_pixel, fb->pixel(x, y));
+            raw_pixel += pixelConverter.length;
+        }
 
+        write(line_buffer.data(), line_buffer.size());
+    }
 }
 
 void
 VncServer::sendFrameBufferResized()
 {
-    assert(fbPtr && dataFd > 0 && curState == NormalPhase);
+    assert(fb && dataFd > 0 && curState == NormalPhase);
     DPRINTF(VNC, "Sending framebuffer resize\n");
 
     FrameBufferUpdate fbu;
@@ -692,19 +702,23 @@ VncServer::sendFrameBufferResized()
 }
 
 void
-VncServer::setFrameBufferParams(VideoConvert::Mode mode, uint16_t width,
-    uint16_t height)
+VncServer::setDirty()
 {
-    VncInput::setFrameBufferParams(mode, width, height);
-
-    if (mode != videoMode || width != videoWidth() || height != videoHeight()) {
-        if (dataFd > 0 && fbPtr && curState == NormalPhase) {
-            if (supportsResizeEnc)
-                sendFrameBufferResized();
-            else
-                // The frame buffer changed size and we can't update the client
-                detach();
-        }
+    VncInput::setDirty();
+
+    sendUpdate = true;
+    sendFrameBufferUpdate();
+}
+
+void
+VncServer::frameBufferResized()
+{
+    if (dataFd > 0 && curState == NormalPhase) {
+        if (supportsResizeEnc)
+            sendFrameBufferResized();
+        else
+            // The frame buffer changed size and we can't update the client
+            detach();
     }
 }