ui: move all C lvgl/zig code into lvgl.zig and drv.zig

the idea is for all zig code to use C LVGL only via this
new module lvgl.zig, all display and input driver/devices is handled
by drv.zig.

this makes C/zig nicely compartmentalized in just a handful places.

build.zig

@@ -8,6 +8,8 @@ pub fn build(b: *std.build.Builder) void {
     const drv = b.option(DriverTarget, "driver", "display and input drivers combo; default: sdl2") orelse .sdl2;
     const disp_horiz = b.option(u32, "horiz", "display horizontal pixels count; default: 800") orelse 800;
     const disp_vert = b.option(u32, "vert", "display vertical pixels count; default: 480") orelse 480;
+    const bopts = b.addOptions();
+    bopts.addOption(DriverTarget, "driver", drv);
 
     // gui build
     const ngui = b.addExecutable("ngui", "src/ngui.zig");
@@ -16,6 +18,7 @@ pub fn build(b: *std.build.Builder) void {
     ngui.pie = true;
     ngui.strip = strip;
 
+    ngui.addPackage(bopts.getPackage("build_options"));
     ngui.addIncludePath("lib");
     ngui.addIncludePath("src/ui/c");
     ngui.linkLibC();
@@ -80,6 +83,7 @@ pub fn build(b: *std.build.Builder) void {
     nd.pie = true;
     nd.strip = strip;
 
+    nd.addPackage(bopts.getPackage("build_options"));
     nifbuild.addPkg(b, nd, "lib/nif");
     const niflib = nifbuild.library(b, "lib/nif");
     niflib.setTarget(target);

src/ngui.zig

@@ -5,6 +5,8 @@ const Thread = std.Thread;
 
 const comm = @import("comm.zig");
 const types = @import("types.zig");
+const ui = @import("ui/ui.zig");
+const lvgl = @import("ui/lvgl.zig");
 const symbol = @import("ui/symbol.zig");
 
 /// SIGPIPE is triggered when a process attempts to write to a broken pipe.
@@ -16,17 +18,7 @@ pub const keep_sigpipe = true;
 const stdin = std.io.getStdIn().reader();
 const stdout = std.io.getStdOut().writer();
 const logger = std.log.scoped(.ngui);
-const lvgl_logger = std.log.scoped(.lvgl); // logs LV_LOG_xxx messages
 
-extern "c" fn lv_timer_handler() u32;
-extern "c" fn lv_log_register_print_cb(*const fn (msg: [*:0]const u8) callconv(.C) void) void;
-const LvTimer = opaque {};
-const LvTimerCallback = *const fn (timer: *LvTimer) callconv(.C) void;
-extern "c" fn lv_timer_create(callback: LvTimerCallback, period_ms: u32, userdata: ?*anyopaque) *LvTimer;
-extern "c" fn lv_timer_del(timer: *LvTimer) void;
-extern "c" fn lv_timer_set_repeat_count(timer: *LvTimer, n: i32) void;
-
-extern "c" fn ui_init() c_int;
 extern "c" fn ui_update_network_status(text: [*:0]const u8, wifi_list: ?[*:0]const u8) void;
 
 /// global heap allocator used throughout the gui program.
@@ -54,11 +46,6 @@ export fn nm_get_curr_tick() u32 {
     return @truncate(u32, ms);
 }
 
-export fn nm_lvgl_log(msg: [*:0]const u8) void {
-    const s = mem.span(msg);
-    lvgl_logger.debug("{s}", .{mem.trimRight(u8, s, "\n")});
-}
-
 /// initiate system shutdown.
 export fn nm_sys_shutdown() void {
     logger.info("initiating system shutdown", .{});
@@ -73,8 +60,8 @@ export fn nm_tab_settings_active() void {
     comm.write(gpa, stdout, msg) catch |err| logger.err("nm_tab_settings_active: {any}", .{err});
 }
 
-export fn nm_request_network_status(t: *LvTimer) void {
-    lv_timer_del(t);
+export fn nm_request_network_status(t: *lvgl.LvTimer) void {
+    lvgl.lv_timer_del(t);
     const msg: comm.Message = .{ .get_network_report = .{ .scan = false } };
     comm.write(gpa, stdout, msg) catch |err| logger.err("nm_request_network_status: {any}", .{err});
 }
@@ -127,8 +114,11 @@ fn updateNetworkStatus(report: comm.Message.NetworkReport) !void {
     // can happen with a fresh connection while dhcp is still in progress.
     if (report.wifi_ssid != null and report.ipaddrs.len == 0) {
         // TODO: sometimes this is too fast, not all ip addrs are avail (ipv4 vs ipv6)
-        var t = lv_timer_create(nm_request_network_status, 1000, null);
-        lv_timer_set_repeat_count(t, 1);
+        if (lvgl.lv_timer_create(nm_request_network_status, 1000, null)) |t| {
+            lvgl.lv_timer_set_repeat_count(t, 1);
+        } else {
+            logger.err("lv_timer_create network status failed: OOM?", .{});
+        }
     }
 }
 
@@ -179,21 +169,21 @@ pub fn main() anyerror!void {
     };
     gpa = gpa_state.allocator();
 
-    // info level log messages are by default printed only in Debug and ReleaseSafe build modes.
-    lv_log_register_print_cb(nm_lvgl_log);
-
-    const c_res = ui_init();
-    if (c_res != 0) {
-        logger.err("ui_init failed with code {}", .{c_res});
+    // initalizes display, input driver and finally creates the user interface.
+    ui.init() catch |err| {
+        logger.err("ui.init: {any}", .{err});
         std.process.exit(1);
-    }
+    };
+
+    // start comms with daemon in a seaparate thread.
     const th = try Thread.spawn(.{}, commThread, .{});
     th.detach();
 
+    // main UI thread; must never block unless in idle/sleep mode
     // TODO: handle sigterm
     while (true) {
         ui_mutex.lock();
-        var till_next_ms = lv_timer_handler();
+        var till_next_ms = lvgl.lv_timer_handler();
         const do_quit = quit;
         ui_mutex.unlock();
         if (do_quit) {

src/ui/c/drv_fbev.c

@@ -8,7 +8,8 @@
 
 #define DISP_BUF_SIZE (NM_DISP_HOR * NM_DISP_VER / 10)
 
-lv_disp_t *drv_init(void)
+/* returns NULL on error */
+lv_disp_t *nm_disp_init(void)
 {
     fbdev_init();
 
@@ -28,29 +29,30 @@ lv_disp_t *drv_init(void)
     disp_drv.ver_res = NM_DISP_VER;
     disp_drv.antialiasing = 1;
     disp_drv.flush_cb = fbdev_flush;
-    lv_disp_t *disp = lv_disp_drv_register(&disp_drv);
-    if (disp == NULL) {
-        return NULL;
-    }
+    return lv_disp_drv_register(&disp_drv);
+}
+
+int nm_indev_init(void)
+{
+    /* lv driver correctly closes and opens evdev again if already inited */
+    evdev_init();
 
     /* keypad input devices default group;
      * future-proof: don't have any atm */
     lv_group_t *g = lv_group_create();
     if (g == NULL) {
-        return NULL;
+        return -1;
     }
     lv_group_set_default(g);
 
-    evdev_init();
     static lv_indev_drv_t touchpad_drv;
     lv_indev_drv_init(&touchpad_drv);
     touchpad_drv.type = LV_INDEV_TYPE_POINTER;
     touchpad_drv.read_cb = evdev_read;
     lv_indev_t *touchpad = lv_indev_drv_register(&touchpad_drv);
     if (touchpad == NULL) {
-        /* TODO: or continue without the touchpad? */
-        return NULL;
+        return -1;
     }
 
-    return disp;
+    return 0;
 }

src/ui/c/drv_sdl2.c

@@ -9,7 +9,7 @@
 #define SDL_MAIN_HANDLED /* suppress "undefined reference to WinMain" */
 #include SDL_INCLUDE_PATH
 
-lv_disp_t *drv_init(void)
+lv_disp_t *nm_disp_init(void)
 {
     sdl_init();
     SDL_DisplayMode dm;
@@ -39,11 +39,11 @@ lv_disp_t *drv_init(void)
     disp_drv.hor_res = NM_DISP_HOR;
     disp_drv.ver_res = NM_DISP_VER;
     disp_drv.antialiasing = 1;
-    lv_disp_t *disp = lv_disp_drv_register(&disp_drv);
-    if (disp == NULL) {
-        return NULL;
-    }
+    return lv_disp_drv_register(&disp_drv);
+}
 
+int nm_indev_init(void)
+{
     static lv_indev_drv_t mouse_drv;
     lv_indev_drv_init(&mouse_drv);
     mouse_drv.type = LV_INDEV_TYPE_POINTER;
@@ -51,15 +51,16 @@ lv_disp_t *drv_init(void)
     lv_indev_t *mouse = lv_indev_drv_register(&mouse_drv);
     if (mouse == NULL) {
         LV_LOG_WARN("lv_indev_drv_register(&mouse_drv) returned NULL");
+        return -1;
     }
 
     /* keypad input devices default group */
     lv_group_t *g = lv_group_create();
     if (g == NULL) {
         LV_LOG_WARN("lv_group_create returned NULL; won't set default group");
-    } else {
-        lv_group_set_default(g);
+        return -1;
     }
+    lv_group_set_default(g);
 
     static lv_indev_drv_t keyboard_drv;
     lv_indev_drv_init(&keyboard_drv);
@@ -68,9 +69,9 @@ lv_disp_t *drv_init(void)
     lv_indev_t *kb = lv_indev_drv_register(&keyboard_drv);
     if (kb == NULL) {
         LV_LOG_WARN("lv_indev_drv_register(&keyboard_drv) returned NULL");
-    } else if (g) {
-        lv_indev_set_group(kb, g);
+        return -1;
     }
+    lv_indev_set_group(kb, g);
 
-    return disp;
+    return 0;
 }

src/ui/c/ui.c

@@ -7,8 +7,6 @@
 #include <stdlib.h>
 #include <unistd.h>
 
-lv_disp_t *drv_init(void);
-
 static lv_style_t style_title;
 static lv_style_t style_text_muted;
 static lv_style_t style_btn_red;
@@ -260,13 +258,8 @@ static void tab_changed_event_cb(lv_event_t *e)
     }
 }
 
-extern int ui_init()
+extern int nm_ui_init(lv_disp_t *disp)
 {
-    lv_init();
-    lv_disp_t *disp = drv_init();
-    if (disp == NULL) {
-        return -1;
-    }
     /* default theme is static */
     lv_theme_t *theme = lv_theme_default_init(disp, /**/
         lv_palette_main(LV_PALETTE_BLUE),           /* primary */

src/ui/drv.zig

@@ -0,0 +1,28 @@
+///! input and display drivers support in zig.
+const std = @import("std");
+const buildopts = @import("build_options");
+
+const lvgl = @import("lvgl.zig");
+
+const logger = std.log.scoped(.drv);
+
+extern "c" fn nm_disp_init() ?*lvgl.LvDisp;
+extern "c" fn nm_indev_init() c_int;
+
+/// initalize a display and make it active for the UI to use.
+/// requires lvgl.init() to have been already called.
+// TODO: rewrite lv_drivers/display/fbdev.c to make fbdev_init return an error
+pub fn initDisplay() !*lvgl.LvDisp {
+    if (nm_disp_init()) |disp| {
+        return disp;
+    }
+    return error.DisplayInitFailed;
+}
+
+/// initialize input devices: touch screen and possibly keyboard if using SDL.
+pub fn initInput() !void {
+    const res = nm_indev_init();
+    if (res != 0) {
+        return error.InputInitFailed;
+    }
+}

src/ui/lvgl.zig

@@ -0,0 +1,59 @@
+///! LVGL types in zig
+const std = @import("std");
+
+/// initalize LVGL internals.
+/// must be called before any other UI functions.
+pub fn init() void {
+    init_once.call();
+}
+
+var init_once = std.once(lvglInit);
+
+fn lvglInit() void {
+    lv_log_register_print_cb(nm_lvgl_log);
+    lv_init();
+}
+
+// logs LV_LOG_xxx messages from LVGL lib
+const lvgl_logger = std.log.scoped(.lvgl);
+
+export fn nm_lvgl_log(msg: [*:0]const u8) void {
+    const s = std.mem.span(msg);
+    // info level log messages are by default printed only in Debug and ReleaseSafe build modes.
+    lvgl_logger.debug("{s}", .{std.mem.trimRight(u8, s, "\n")});
+}
+
+extern "c" fn lv_init() void;
+extern "c" fn lv_log_register_print_cb(*const fn (msg: [*:0]const u8) callconv(.C) void) void;
+
+/// represents lv_timer_t in C.
+pub const LvTimer = opaque {};
+pub const LvTimerCallback = *const fn (timer: *LvTimer) callconv(.C) void;
+/// the timer handler is the LVGL busy-wait loop iteration.
+pub extern "c" fn lv_timer_handler() u32;
+pub extern "c" fn lv_timer_create(callback: LvTimerCallback, period_ms: u32, userdata: ?*anyopaque) ?*LvTimer;
+pub extern "c" fn lv_timer_del(timer: *LvTimer) void;
+pub extern "c" fn lv_timer_set_repeat_count(timer: *LvTimer, n: i32) void;
+
+/// represents lv_obj_t type in C.
+pub const LvObj = opaque {};
+/// delete and deallocate an object and all its children from UI tree.
+pub extern "c" fn lv_obj_del(obj: *LvObj) void;
+
+/// represents lv_indev_t in C, an input device such as touchscreen or a keyboard.
+pub const LvIndev = opaque {};
+/// deallocate and delete an input device from LVGL registry.
+pub extern "c" fn lv_indev_delete(indev: *LvIndev) void;
+/// return next device in the list or head if indev is null.
+pub extern "c" fn lv_indev_get_next(indev: ?*LvIndev) ?*LvIndev;
+
+/// represents lv_disp_t in C.
+pub const LvDisp = opaque {};
+/// return elapsed time since last user activity on a specific display
+/// or any if disp is null.
+pub extern "c" fn lv_disp_get_inactive_time(disp: ?*LvDisp) u32;
+/// make it so as if a user activity happened.
+/// this resets an internal counter in lv_disp_get_inactive_time.
+pub extern "c" fn lv_disp_trig_activity(disp: ?*LvDisp) void;
+/// force redraw dirty areas.
+pub extern "c" fn lv_refr_now(disp: ?*LvDisp) void;

src/ui/ui.zig

@@ -0,0 +1,22 @@
+const std = @import("std");
+
+const lvgl = @import("lvgl.zig");
+const drv = @import("drv.zig");
+
+const logger = std.log.scoped(.ui);
+
+extern "c" fn nm_ui_init(disp: *lvgl.LvDisp) c_int;
+
+pub fn init() !void {
+    lvgl.init();
+    const disp = try drv.initDisplay();
+    drv.initInput() catch |err| {
+        // TODO: or continue without the touchpad?
+        // at the very least must disable screen blanking timeout in case of a failure.
+        // otherwise, impossible to wake up the screen. */
+        return err;
+    };
+    if (nm_ui_init(disp) != 0) {
+        return error.UiInitFailure;
+    }
+}