From 00d22febd2c73f5ccb058ca2211294b1a1d99e9c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20Ankarstr=C3=B6m?= <john@ankarstrom.se>
Date: Wed, 27 Apr 2022 16:06:42 +0200
Subject: Press left/right to select next/previous unwatched episode.

---
 c/defs.h             |  1 +
 c/episodelistview.c  | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 pl/track_episodes.pl | 18 +++++++++++++++-
 3 files changed, 78 insertions(+), 1 deletion(-)

diff --git a/c/defs.h b/c/defs.h
index 14b7626..1e463dd 100644
--- a/c/defs.h
+++ b/c/defs.h
@@ -21,6 +21,7 @@ LRESULT ElvHandleNotify(LPARAM);
 void ElvRedraw(void);
 void ElvSetTop(int);
 void ElvSelectRecent(void);
+void ElvSelectUnwatched(int);
 void ElvUpdate(void);
 void ElvUpdateItem(LPLVITEM);
 
diff --git a/c/episodelistview.c b/c/episodelistview.c
index 08bd0db..ad32b81 100644
--- a/c/episodelistview.c
+++ b/c/episodelistview.c
@@ -80,6 +80,20 @@ ElvHandleNotify(LPARAM lParam)
 	    s:	ElvDoSort();
 		break;
 	    }
+	case LVN_KEYDOWN:	/* Navigate episodes by keyboard. */
+	    {
+		LPNMLVKEYDOWN lpNmLvKd;
+		lpNmLvKd = (LPNMLVKEYDOWN)lParam;
+		switch (lpNmLvKd->wVKey) {
+		case VK_LEFT:
+			ElvSelectUnwatched(-1);
+			break;
+		case VK_RIGHT:
+			ElvSelectUnwatched(1);
+			break;
+		}
+		break;
+	    }
 	case NM_CUSTOMDRAW:	/* Make unwatched episodes bold. */
 	    {
 		LPNMLVCUSTOMDRAW lpLvCd;
@@ -196,6 +210,51 @@ s:	ListView_SetItemState(HElv, -1, LVIF_STATE, LVIS_SELECTED);
 	DlvShowEpisode(iEpisode);
 }
 
+/* Select next/previous unwatched episode. */
+void
+ElvSelectUnwatched(int iDir)
+{
+	int bShift, i, iEpNew, iItemNew;
+	LVFINDINFO lvfi;
+	LVITEM lviFocus;
+	term_t t;
+
+	/* Get focused episode. */
+	lviFocus.mask = LVIF_PARAM;
+	lviFocus.iItem = -1;
+	while ((lviFocus.iItem = ListView_GetNextItem(
+		    HElv, lviFocus.iItem, LVNI_FOCUSED)) != -1) {
+		if (!ListView_GetItem(HElv, &lviFocus)) continue;
+	}
+
+	i = 0;
+	lvfi.flags = LVFI_PARAM;
+	lvfi.lParam = lviFocus.lParam;
+	bShift = GetAsyncKeyState(VK_SHIFT);
+
+	do {
+		t = T(2);
+		PI(t,lvfi.lParam) return;
+		P("track_episodes",iDir > 0? "next_unwatched": "previous_unwatched",2,t)
+			return;
+		GI(t+1,&iEpNew) return;
+
+		lvfi.lParam = iEpNew;
+		if ((iItemNew = ListView_FindItem(HElv, -1, &lvfi)) != -1) {
+			if (!bShift) {
+				ListView_SetItemState(HElv, -1,
+				    LVIF_STATE, LVIS_SELECTED);
+			}
+			ListView_SetItemState(HElv, iItemNew,
+			    LVIS_SELECTED|LVIS_FOCUSED,
+			    LVIS_SELECTED|LVIS_FOCUSED);
+			ElvRedraw();
+			ListView_EnsureVisible(HElv, iItemNew, TRUE);
+			return;
+		}
+	} while (i++ < 1000);
+}
+
 /* Sort list view items, iSort being the 1-based index of the column
  * to sort by. If iSort is negative, the order is descending. */
 int CALLBACK
@@ -288,6 +347,7 @@ ElvUpdate()
 
 	/* Save focus. */
 	iEpFocus = 0;
+	lvi.iItem = -1;
 	while ((lvi.iItem = ListView_GetNextItem(
 		    HElv, lvi.iItem, LVNI_FOCUSED)) != -1) {
 		if (!ListView_GetItem(HElv, &lvi)) continue;
diff --git a/pl/track_episodes.pl b/pl/track_episodes.pl
index f18e85c..1973a75 100644
--- a/pl/track_episodes.pl
+++ b/pl/track_episodes.pl
@@ -2,7 +2,9 @@
 			   toggle_episode/1,
 			   forget_episode/1,
 			   most_recently_watched/1,
-			   watched/1]).
+			   watched/1,
+			   next_unwatched/2,
+			   previous_unwatched/2]).
 
 :- use_module(library(dcg/basics)).
 :- use_module(library(registry)).
@@ -94,3 +96,17 @@ most_recently_watched(Ep) :-
 
 watched(Ep) :-
 	episode_watched(Ep, true).
+
+next_unwatched(Ep0, Ep) :-
+	Ep1 is Ep0 + 1,
+	(   \+ watched(Ep1)
+	->  Ep = Ep1
+	;   next_unwatched(Ep1, Ep)
+	).
+
+previous_unwatched(Ep0, Ep) :-
+	Ep1 is Ep0 - 1,
+	(   \+ watched(Ep1)
+	->  Ep = Ep1
+	;   previous_unwatched(Ep1, Ep)
+	).
-- 
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