From 596ec20dd81fc4a48a528bfed9e241343ee03eaa Mon Sep 17 00:00:00 2001
From: Rudy Dellomas III <dther@dther.xyz>
Date: Sun, 21 Apr 2024 20:25:40 +1000
Subject: Emit an event (ui_draw) immediately before drawing the screen

This allows better control over styling, as well as potential for
entirely new UI elements implemented entirely using the Lua API.
---
 lua/vis.lua   |  2 ++
 main.c        |  1 +
 ui-terminal.c |  1 +
 vis-core.h    |  1 +
 vis-lua.c     | 14 +++++++++++++-
 vis-lua.h     |  1 +
 vis.c         |  4 ++++
 vis.h         |  1 +
 8 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/lua/vis.lua b/lua/vis.lua
index 32fb2a1..5473f17 100644
--- a/lua/vis.lua
+++ b/lua/vis.lua
@@ -167,6 +167,7 @@ local events = {
 	WIN_STATUS = "Event::WIN_STATUS", -- see @{win_status}
 	TERM_CSI = "Event::TERM_CSI", -- see @{term_csi}
 	PROCESS_RESPONSE = "Event::PROCESS_RESPONSE", -- see @{process_response}
+	UI_DRAW = "Event::UI_DRAW", -- see @{ui_draw}
 }
 
 events.file_close = function(...) events.emit(events.FILE_CLOSE, ...) end
@@ -183,6 +184,7 @@ events.win_open = function(...) events.emit(events.WIN_OPEN, ...) end
 events.win_status = function(...) events.emit(events.WIN_STATUS, ...) end
 events.term_csi = function(...) events.emit(events.TERM_CSI, ...) end
 events.process_response = function(...) events.emit(events.PROCESS_RESPONSE, ...) end
+events.ui_draw = function(...) events.emit(events.UI_DRAW, ...) end
 
 local handlers = {}
 
diff --git a/main.c b/main.c
index 8e5ad42..8aa31c6 100644
--- a/main.c
+++ b/main.c
@@ -2229,6 +2229,7 @@ int main(int argc, char *argv[]) {
 		.win_highlight = vis_lua_win_highlight,
 		.win_status = vis_lua_win_status,
 		.term_csi = vis_lua_term_csi,
+		.ui_draw = vis_lua_ui_draw,
 	};
 
 	vis = vis_new(ui_term_new(), &event);
diff --git a/ui-terminal.c b/ui-terminal.c
index 6ec1e41..09e618e 100644
--- a/ui-terminal.c
+++ b/ui-terminal.c
@@ -392,6 +392,7 @@ static void ui_draw(Ui *ui) {
 		ui_window_draw((UiWin*)win);
 	if (tui->info[0])
 		ui_draw_string(tui, 0, tui->height-1, tui->info, NULL, UI_STYLE_INFO);
+	vis_event_emit(tui->vis, VIS_EVENT_UI_DRAW);
 	ui_term_backend_blit(tui);
 }
 
diff --git a/vis-core.h b/vis-core.h
index 8d3980c..4f81e4c 100644
--- a/vis-core.h
+++ b/vis-core.h
@@ -236,6 +236,7 @@ enum VisEvents {
 	VIS_EVENT_WIN_HIGHLIGHT,
 	VIS_EVENT_WIN_STATUS,
 	VIS_EVENT_TERM_CSI,
+	VIS_EVENT_UI_DRAW,
 };
 
 bool vis_event_emit(Vis*, enum VisEvents, ...);
diff --git a/vis-lua.c b/vis-lua.c
index 3d80293..91ee428 100644
--- a/vis-lua.c
+++ b/vis-lua.c
@@ -166,7 +166,7 @@ void vis_lua_win_status(Vis *vis, Win *win) { window_status_update(vis, win); }
 void vis_lua_term_csi(Vis *vis, const long *csi) { }
 void vis_lua_process_response(Vis *vis, const char *name,
                               char *buffer, size_t len, ResponseType rtype) { }
-
+void vis_lua_ui_draw(Vis *vis) { }
 
 #else
 
@@ -3689,4 +3689,16 @@ void vis_lua_process_response(Vis *vis, const char *name,
 	lua_pop(L, 1);
 }
 
+/***
+ * Emitted immediately before the UI is drawn to the screen.
+ * Allows last-minute overrides to the styling of UI elements.
+ *
+ * *WARNING:* This is emitted every screen draw!
+ * Use sparingly and check for `nil` values!
+ * @function ui_draw
+ */
+void vis_lua_ui_draw(Vis *vis) {
+	vis_lua_event_call(vis, "ui_draw");
+}
+
 #endif
diff --git a/vis-lua.h b/vis-lua.h
index d622ff5..b4f3f51 100644
--- a/vis-lua.h
+++ b/vis-lua.h
@@ -42,5 +42,6 @@ void vis_lua_win_highlight(Vis*, Win*);
 void vis_lua_win_status(Vis*, Win*);
 void vis_lua_term_csi(Vis*, const long *);
 void vis_lua_process_response(Vis *, const char *, char *, size_t, ResponseType);
+void vis_lua_ui_draw(Vis*);
 
 #endif
diff --git a/vis.c b/vis.c
index e287405..0c05558 100644
--- a/vis.c
+++ b/vis.c
@@ -105,6 +105,10 @@ bool vis_event_emit(Vis *vis, enum VisEvents id, ...) {
 		if (vis->event->term_csi)
 			vis->event->term_csi(vis, va_arg(ap, const long *));
 		break;
+	case VIS_EVENT_UI_DRAW:
+		if (vis->event->ui_draw)
+			vis->event->ui_draw(vis);
+		break;
 	}
 
 	va_end(ap);
diff --git a/vis.h b/vis.h
index b67d3c5..8287a45 100644
--- a/vis.h
+++ b/vis.h
@@ -58,6 +58,7 @@ typedef struct {
 	void (*win_highlight)(Vis*, Win*);
 	void (*win_status)(Vis*, Win*);
 	void (*term_csi)(Vis*, const long *);
+	void (*ui_draw)(Vis*);
 } VisEvent;
 
 /** Union used to pass arguments to key action functions. */
-- 
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