Patch gui_fb to work at high-resolutions

packages/genodelabs/depot-targets.nix

@@ -88,7 +88,7 @@ in {
   gpt_write.portInputs = with ports; [ jitterentropy ];
   grep = { };
   gui_fader = { };
-  gui_fb = { };
+  gui_fb.patches = [ ./patches/gui_fb.patch ];
   icu = { };
   imx53_qsb_drivers = { };
   imx8_fb_drv = { };

packages/genodelabs/patches/gui_fb.patch

@@ -0,0 +1,59 @@
+From 92f7d224725ef3952924e230d2b41b58c043b9e3 Mon Sep 17 00:00:00 2001
+From: Emery Hemingway <ehmry@posteo.net>
+Date: Wed, 14 Apr 2021 11:51:38 +0200
+Subject: [PATCH] gui_fb: always set a usable framebuffer mode
+
+Reduce the size of a requested mode until there is sufficient RAM
+to render that mode, rather than refuse to set a mode at all.
+---
+ repos/os/src/server/gui_fb/main.cc | 20 +++++++++++++-------
+ 1 file changed, 13 insertions(+), 7 deletions(-)
+
+diff --git a/repos/os/src/server/gui_fb/main.cc b/repos/os/src/server/gui_fb/main.cc
+index 923208896e..8ce9710224 100644
+--- a/repos/os/src/server/gui_fb/main.cc
++++ b/repos/os/src/server/gui_fb/main.cc
+@@ -121,7 +121,7 @@ struct Framebuffer::Session_component : Genode::Rpc_object<Framebuffer::Session>
+ 
+ 	bool _dataspace_is_new = true;
+ 
+-	bool _ram_suffices_for_mode(Framebuffer::Mode mode) const
++	bool ram_suffices_for_mode(Framebuffer::Mode mode) const
+ 	{
+ 		/* calculation in bytes */
+ 		size_t const used      = _buffer_num_bytes,
+@@ -153,11 +153,6 @@ struct Framebuffer::Session_component : Genode::Rpc_object<Framebuffer::Session>
+ 
+ 		Framebuffer::Mode const mode { .area = size };
+ 
+-		if (!_ram_suffices_for_mode(mode)) {
+-			Genode::warning("insufficient RAM for mode ", mode);
+-			return;
+-		}
+-
+ 		_next_mode = mode;
+ 
+ 		if (_mode_sigh.valid())
+@@ -372,7 +367,18 @@ struct Nit_fb::Main : View_updater
+ 			if (height < 0) height = gui_height + height;
+ 		}
+ 
+-		fb_session.size(Area(width, height));
++		Framebuffer::Mode mode { .area = Area(width, height) };
++
++		if (!fb_session.ram_suffices_for_mode(mode))
++			Genode::warning("insufficient RAM for mode ", mode);
++
++		while (!fb_session.ram_suffices_for_mode(mode)) {
++			mode.area = Area(
++				(mode.area.w() / 4) * 3,
++				(mode.area.h() / 4) * 3);
++		}
++
++		fb_session.size(mode.area);
+ 	}
+ 
+ 	void handle_config_update()
+-- 
+2.31.0
+