st-scrollback-mouse-altscreen-20200416-5703aa0.diff

diff --git a/config.def.h b/config.def.h
index 4b3bf15..1986316 100644
--- a/config.def.h
+++ b/config.def.h
@@ -163,8 +163,8 @@ static uint forcemousemod = ShiftMask;
  */
 static MouseShortcut mshortcuts[] = {
 	/* mask                 button   function        argument       release */
-	{ ShiftMask,            Button4, kscrollup,      {.i = 1} },
-	{ ShiftMask,            Button5, kscrolldown,    {.i = 1} },
+	{ XK_ANY_MOD,           Button4, kscrollup,      {.i = 1},      0, /* !alt */ -1 },
+	{ XK_ANY_MOD,           Button5, kscrolldown,    {.i = 1},      0, /* !alt */ -1 },
 	{ XK_ANY_MOD,           Button2, selpaste,       {.i = 0},      1 },
 	{ XK_ANY_MOD,           Button4, ttysend,        {.s = "\031"} },
 	{ XK_ANY_MOD,           Button5, ttysend,        {.s = "\005"} },
diff --git a/st.c b/st.c
index f8b6f67..dd4cb31 100644
--- st.c
+++ st.c
@@ -1045,6 +1045,11 @@ tnew(int col, int row)
 	treset();
 }
 
+int tisaltscr(void)
+{
+	return IS_SET(MODE_ALTSCREEN);
+}
+
 void
 tswapscreen(void)
 {
diff --git a/st.h b/st.h
index 1332cf1..f9ad815 100644
--- st.h
+++ st.h
@@ -89,6 +89,7 @@ void sendbreak(const Arg *);
 void toggleprinter(const Arg *);
 
 int tattrset(int);
+int tisaltscr(void);
 void tnew(int, int);
 void tresize(int, int);
 void tsetdirtattr(int);
diff --git a/x.c b/x.c
index e5f1737..b8fbd7b 100644
--- x.c
+++ x.c
@@ -34,6 +34,7 @@ typedef struct {
 	void (*func)(const Arg *);
 	const Arg arg;
 	uint  release;
+	int  altscrn;  /* 0: don't care, -1: not alt screen, 1: alt screen */
 } MouseShortcut;
 
 typedef struct {
@@ -446,6 +447,7 @@ mouseaction(XEvent *e, uint release)
 	for (ms = mshortcuts; ms < mshortcuts + LEN(mshortcuts); ms++) {
 		if (ms->release == release &&
 		    ms->button == e->xbutton.button &&
+		    (!ms->altscrn || (ms->altscrn == (tisaltscr() ? 1 : -1))) &&
 		    (match(ms->mod, state) ||  /* exact or forced */
 		     match(ms->mod, state & ~forcemousemod))) {
 			ms->func(&(ms->arg));