LCD core move buf ptr and address look up function viewport struct

I'm currently running up against the limitations of the lcd_draw functions
I want these functions to be able to be used on any size buffer not
just buffers with a stride matching the underlying device

[DONE] allow the framebuffer to be decoupled from the device framebuffer
[DONE need examples] allow for some simple blit like transformations
[DONE] remove the device framebuffer from the plugin api
[DONE}ditto remote framebuffer
[DONE] remove _viewport_get_framebuffer you can call struct *vp = lcd_set_viewport(NULL) and vp->buffer->fb_ptr

while remote lcds may compile (and work in the sim) its not been tested on targets

[FIXED] backdrops need work to be screen agnostic

[FIXED] screen statusbar is not being combined into the main viewport correctly yet

[FIXED] screen elements are displayed incorrectly  after switch to void*

[FIXED] core didn't restore proper viewport on splash etc.

[NEEDS TESTING] remote lcd garbled data

[FIXED] osd lib garbled screen on bmp_part

[FIXED] grey_set_vp needs to return old viewport like lcd_set_viewport

[FIXED] Viewport update now handles viewports with differing buffers/strides by copying to the main buffer

[FIXED] splash on top of WPS leaves old framebuffer data (doesn't redraw)
[UPDATE] refined this a bit more to have clear_viewport set the clean bit and have skin_render do its own screen clear
scrolling viewports no longer trigger wps refresh
also fixed a bug where guisyncyesno was displaying and then disappearing

[ADDED!] New LCD macros that allow you to create properly size frame buffers in you desired size without wasting bytes
(LCD_ and LCD_REMOTE_)
LCD_STRIDE(w, h) same as STRIDE_MAIN
LCD_FBSTRIDE(w, h) returns target specific stride for a buffer W x H
LCD_NBELEMS(w, h) returns the number of fb_data sized elemenst needed for a buffer W x H
LCD_NATIVE_STRIDE(s) conversion between rockbox native vertical and lcd native stride (2bitH)
test_viewports.c has an example of usage

[FIXED!!] 2bit targets don't respect non-native strides
[FIXED] Few define snags

Change-Id: I0d04c3834e464eca84a5a715743a297a0cefd0af

1 files changed, 21 insertions, 4 deletions

diff --git a/apps/gui/skin_engine/skin_backdrops.c b/apps/gui/skin_engine/skin_backdrops.c
index 243fc30a3a..caf705af54 100644
--- a/apps/gui/skin_engine/skin_backdrops.c
+++ b/apps/gui/skin_engine/skin_backdrops.c
@@ -204,11 +204,28 @@ bool skin_backdrops_preload(void)
     return retval;
 }
 
-void* skin_backdrop_get_buffer(int backdrop_id)
+void skin_backdrop_set_buffer(int backdrop_id, struct skin_viewport *svp)
 {
-    if (backdrop_id < 0)
-        return NULL;
-    return backdrops[backdrop_id].buffer;
+    if (UNLIKELY(!svp))
+        return;
+    else if (backdrop_id < 0)
+    {
+        svp->vp.buffer = NULL; /*Default*/
+        return;
+    }
+
+    enum screen_type screen = backdrops[backdrop_id].screen;
+    svp->framebuf.ch_ptr = backdrops[backdrop_id].buffer;
+#if defined(HAVE_REMOTE_LCD)
+    if (screen == SCREEN_REMOTE)
+        svp->framebuf.elems = REMOTE_LCD_BACKDROP_BYTES / sizeof(fb_remote_data);
+    else
+#endif
+    {
+        svp->framebuf.elems = LCD_BACKDROP_BYTES / sizeof(fb_data);
+    }
+    svp->framebuf.get_address_fn = NULL; /*Default iterator*/
+    screens[screen].viewport_set_buffer(&svp->vp, &svp->framebuf);
 }
 
 void skin_backdrop_show(int backdrop_id)