Fix margins for GameBox Mini (#104)

* Fix margin to have a black bar instead of garbage on the metal case

This unit came in two case variations. The plastic case, which was modified from a simple LCD keyring toy game and for which the unit was designed to fit inside, and a metal case that was designed specifically to house the internals.

Turns out, the viewing window on the metal case is higher than on the plastic case, presumably to make better use of the actual screen. With the previous margin, garbage is shown on the bottom of the screen if playing with a metal case. With the plastic case, the bottom of the screen is physically masked off to prevent light bleed, which is why I didn't notice before. Extending the bottom margin prevents the garbage on the bottom of the metal units.

* Update config.h

Added fixed margin values for plastic case and for metal case.

Author: Cralex

components/retro-go/targets/mrgc-gbm/config.h

@@ -16,10 +16,9 @@
 #define RG_SCREEN_HOST              SPI2_HOST
 #define RG_SCREEN_SPEED             SPI_MASTER_FREQ_40M
 #define RG_SCREEN_WIDTH             240
-#define RG_SCREEN_HEIGHT            230 // Display height 192 plus margin? Was 232
+#define RG_SCREEN_HEIGHT            240
 #define RG_SCREEN_ROTATE            0
 #define RG_SCREEN_MARGIN_TOP        38
-#define RG_SCREEN_MARGIN_BOTTOM     2  // Too little gives you garbage under the bottom bezel.
 #define RG_SCREEN_MARGIN_LEFT       0
 #define RG_SCREEN_MARGIN_RIGHT      0
 #define RG_SCREEN_INIT()                                                                                   \
@@ -35,6 +34,13 @@
     ILI9341_CMD(0xE1, 0xD0, 0x00, 0x05, 0x0D, 0x0C, 0x06, 0x2D, 0x44, 0x40, 0x0E, 0x1C, 0x18, 0x16, 0x19); \
     ILI9341_CMD(0x21);
 
+// Screen margin
+// Uncomment the following line if using a plastic case
+#define RG_SCREEN_MARGIN_BOTTOM     10  // Fullscreen for plastic case. Black bar on bottom for metal case.
+
+// Uncomment the following line if using a metal case
+// #define RG_SCREEN_MARGIN_BOTTOM     0  // Fullscreen for metal case. Cropped on bottom for plastic case.
+
 // Input
 #define RG_GAMEPAD_DRIVER           3   // 1 = ODROID-GO, 2 = Serial, 3 = I2C, 4 = AW9523, 5 = ESPLAY-S3, 6 = SDL2
 #define RG_GAMEPAD_HAS_MENU_BTN     1
@@ -63,7 +69,7 @@
 #define RG_BATTERY_CALC_PERCENT(raw) (((raw) - 170) / 30.f * 100.f)
 #define RG_BATTERY_CALC_VOLTAGE(raw) (0)
 
-// Status LED
+// Status LED (Does not seem to be mappable)
 // #define RG_GPIO_LED                 GPIO_NUM_NC
 // #define RG_GPIO_LED                 GPIO_NUM_13 // From OG Firmware