[gnome-games] flatpak: Use the BlastEm core from Libretro

[Alexander Mikhaylenko <alexm src gnome org>]

commit 9e55926354896a47f12a1b3a4f7b27cb33f424f6
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Fri Dec 11 11:46:30 2020 +0100

    flatpak: Use the BlastEm core from Libretro
    
    It should be in a good enough shape to be used now.
    
    Fixes https://gitlab.gnome.org/GNOME/gnome-games/-/issues/74

 ...lastem-Give-a-saner-default-button-layout.patch | 35 +++++++++++++++
 ...etro-Correctly-calculate-the-aspect-ratio.patch | 52 ++++++++++++++++++++++
 flatpak/libretro-cores/libretro-blastem.json       | 22 +++++----
 flatpak/org.gnome.Games.json                       |  1 +
 4 files changed, 102 insertions(+), 8 deletions(-)
---
diff --git a/flatpak/libretro-cores/blastem-Give-a-saner-default-button-layout.patch 
b/flatpak/libretro-cores/blastem-Give-a-saner-default-button-layout.patch
new file mode 100644
index 00000000..97d3f888
--- /dev/null
+++ b/flatpak/libretro-cores/blastem-Give-a-saner-default-button-layout.patch
@@ -0,0 +1,35 @@
+From dc3a2e8fc3f9d0ea47c7775b89ee167f58a80b13 Mon Sep 17 00:00:00 2001
+From: Adrien Plazas <kekun plazas laposte net>
+Date: Sat, 12 Dec 2020 09:48:29 +0100
+Subject: [PATCH] Give a saner default button layout
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+This gives a saner default layout for 99% of games as nobody wants to
+jump with the R button. This is also better for the vast majority of
+6-buttons games like Streets of Rage 3 or Ranger X, with the notable
+exception of Super Street Fighter II, but who emulates it on the Genesis
+anyways‽
+---
+ libblastem.c | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/libblastem.c b/libblastem.c
+index fb5979a7..280e72ef 100644
+--- a/libblastem.c
++++ b/libblastem.c
+@@ -413,8 +413,8 @@ void process_events()
+ {
+       static int16_t prev_state[2][RETRO_DEVICE_ID_JOYPAD_L2];
+       static const uint8_t map[] = {
+-              BUTTON_A, BUTTON_X, BUTTON_MODE, BUTTON_START, DPAD_UP, DPAD_DOWN,
+-              DPAD_LEFT, DPAD_RIGHT, BUTTON_B, BUTTON_Y, BUTTON_Z, BUTTON_C
++              BUTTON_B, BUTTON_A, BUTTON_MODE, BUTTON_START, DPAD_UP, DPAD_DOWN,
++              DPAD_LEFT, DPAD_RIGHT, BUTTON_C, BUTTON_Y, BUTTON_X, BUTTON_Z
+       };
+       //TODO: handle other input device types
+       //TODO: handle more than 2 ports when appropriate
+-- 
+2.28.0
+
diff --git a/flatpak/libretro-cores/blastem-libretro-Correctly-calculate-the-aspect-ratio.patch 
b/flatpak/libretro-cores/blastem-libretro-Correctly-calculate-the-aspect-ratio.patch
new file mode 100644
index 00000000..26e33cf7
--- /dev/null
+++ b/flatpak/libretro-cores/blastem-libretro-Correctly-calculate-the-aspect-ratio.patch
@@ -0,0 +1,52 @@
+From 8fd95a881fed8ff28b359b4c4d895fe94e7ed707 Mon Sep 17 00:00:00 2001
+From: Adrien Plazas <kekun plazas laposte net>
+Date: Sat, 12 Dec 2020 09:48:29 +0100
+Subject: [PATCH] libretro: Correctly calculate the aspect ratio
+
+This ensures the aspect ratio is correctly calculated at all time, for
+W40 and W32, for NTSC and PAL, and with any overscan.
+
+The calculation was wrong in render_framebuffer_updated().
+---
+ libblastem.c | 11 +++++++++--
+ 1 file changed, 9 insertions(+), 2 deletions(-)
+
+diff --git a/libblastem.c b/libblastem.c
+index 819f2fad..29dc54c6 100644
+--- a/libblastem.c
++++ b/libblastem.c
+@@ -129,6 +129,13 @@ static void update_overscan(void)
+       }
+ }
+ 
++static float get_aspect_ratio(void)
++{
++      float aspect_width = LINEBUF_SIZE - overscan_left - overscan_right;
++      float aspect_height = (video_standard == VID_NTSC ? 243 : 294) - overscan_top - overscan_bot;
++      return aspect_width / aspect_height;
++}
++
+ static int32_t sample_rate;
+ RETRO_API void retro_get_system_av_info(struct retro_system_av_info *info)
+ {
+@@ -138,7 +145,7 @@ RETRO_API void retro_get_system_av_info(struct retro_system_av_info *info)
+       info->geometry.base_height = (video_standard == VID_NTSC ? 243 : 294) - (overscan_top + overscan_bot);
+       last_height = info->geometry.base_height;
+       info->geometry.max_height = info->geometry.base_height * 2;
+-      info->geometry.aspect_ratio = 0;
++      info->geometry.aspect_ratio = get_aspect_ratio();
+       double master_clock = video_standard == VID_NTSC ? 53693175 : 53203395;
+       double lines = video_standard == VID_NTSC ? 262 : 313;
+       info->timing.fps = master_clock / (3420.0 * lines);
+@@ -368,7 +375,7 @@ void render_framebuffer_updated(uint8_t which, int width)
+               struct retro_game_geometry geometry = {
+                       .base_width = width,
+                       .base_height = height,
+-                      .aspect_ratio = (float)LINEBUF_SIZE / base_height
++                      .aspect_ratio = get_aspect_ratio()
+               };
+               retro_environment(RETRO_ENVIRONMENT_SET_GEOMETRY, &geometry);
+               last_width = width;
+-- 
+2.28.0
+
diff --git a/flatpak/libretro-cores/libretro-blastem.json b/flatpak/libretro-cores/libretro-blastem.json
index b04942d3..8d0aad52 100644
--- a/flatpak/libretro-cores/libretro-blastem.json
+++ b/flatpak/libretro-cores/libretro-blastem.json
@@ -5,15 +5,13 @@
                 "arm"
             ],
             "no-autogen": true,
-            "install-rule": "install_libretro",
             "make-args": [
-                "prefix=/app",
-                "core_installdir=/app/lib/libretro",
-                "libblastem.so"
+                "--makefile=Makefile.libretro",
+                "prefix=/app"
             ],
             "make-install-args": [
-                "prefix=/app",
-                "core_installdir=/app/lib/libretro"
+                "--makefile=Makefile.libretro",
+                "prefix=/app"
             ],
             "post-install": [
                 "mkdir -p /app/lib/libretro/",
@@ -22,8 +20,16 @@
             "sources": [
                 {
                     "type": "git",
-                    "url": "https://gitlab.gnome.org/aplazas/blastem.git";,
-                    "branch": "gnome-games"
+                    "url": "https://github.com/libretro/blastem.git";,
+                    "branch": "libretro"
+                },
+                {
+                    "type": "patch",
+                    "path": "blastem-Give-a-saner-default-button-layout.patch"
+                },
+                {
+                    "type": "patch",
+                    "path": "blastem-libretro-Correctly-calculate-the-aspect-ratio.patch"
                 },
                 {
                     "type": "file",
diff --git a/flatpak/org.gnome.Games.json b/flatpak/org.gnome.Games.json
index 4636fad5..40b2a5e1 100644
--- a/flatpak/org.gnome.Games.json
+++ b/flatpak/org.gnome.Games.json
@@ -51,6 +51,7 @@
         "shared-modules/lua5.3/lua-5.3.5.json",
         "shared-modules/SDL/SDL-1.2.15.json",
         "shared-modules/SDL/SDL_net-1.2.8.json",
+        "libretro-cores/libretro-blastem.json",
         "libretro-cores/libretro-bsnes-mercury.json",
         "libretro-cores/libretro-citra.json",
         "libretro-cores/libretro-desmume2015.json",