From 01fe12b2ce9f75790538624aff7acfd8f6bef287 Mon Sep 17 00:00:00 2001
From: Christian Zangl <laktak@cdak.net>
Date: Sun, 8 May 2022 12:58:56 +0200
Subject: [PATCH] Add VIMs hi/mid/lo-screen commands (#824)

* add hi/mid/lo-screen commands and default keybindings

* doc
---
 doc.go       |  9 +++++++++
 docstring.go |  9 +++++++++
 eval.go      | 24 ++++++++++++++++++++++++
 lf.1         | 11 +++++++++++
 nav.go       | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 opts.go      |  3 +++
 6 files changed, 103 insertions(+)

diff --git a/doc.go b/doc.go
index f0e044f..3d3f758 100644
--- a/doc.go
+++ b/doc.go
@@ -31,6 +31,9 @@ The following commands are provided by lf:
     jump-prev                (default '[')
     top                      (default 'gg' and '<home>')
     bottom                   (default 'G' and '<end>')
+    hi-screen                (default 'H')
+    mid-screen               (default 'M')
+    lo-screen                (default 'L')
     toggle
     invert                   (default 'v')
     unselect                 (default 'u')
@@ -295,6 +298,12 @@ Change the current working directory to the next/previous jumplist item.
 
 Move the current file selection to the top/bottom of the directory.
 
+    hi-screen                (default 'H')
+    mid-screen               (default 'M')
+    lo-screen                (default 'L')
+
+Move the current file selection to the top/middle/bottom of the screen.
+
     toggle
 
 Toggle the selection of the current file or files given as arguments.
diff --git a/docstring.go b/docstring.go
index a8829ac..2627f0a 100644
--- a/docstring.go
+++ b/docstring.go
@@ -35,6 +35,9 @@ The following commands are provided by lf:
     jump-prev                (default '[')
     top                      (default 'gg' and '<home>')
     bottom                   (default 'G' and '<end>')
+    hi-screen                (default 'H')
+    mid-screen               (default 'M')
+    lo-screen                (default 'L')
     toggle
     invert                   (default 'v')
     unselect                 (default 'u')
@@ -307,6 +310,12 @@ Change the current working directory to the next/previous jumplist item.
 
 Move the current file selection to the top/bottom of the directory.
 
+    hi-screen                (default 'H')
+    mid-screen               (default 'M')
+    lo-screen                (default 'L')
+
+Move the current file selection to the top/middle/bottom of the screen.
+
     toggle
 
 Toggle the selection of the current file or files given as arguments.
diff --git a/eval.go b/eval.go
index 54f2dcb..00ddb67 100644
--- a/eval.go
+++ b/eval.go
@@ -963,6 +963,30 @@ func (e *callExpr) eval(app *app, args []string) {
 			app.ui.loadFile(app.nav, true)
 			app.ui.loadFileInfo(app.nav)
 		}
+	case "hi-screen":
+		if !app.nav.init {
+			return
+		}
+		if app.nav.hiScreen() {
+			app.ui.loadFile(app.nav, true)
+			app.ui.loadFileInfo(app.nav)
+		}
+	case "mid-screen":
+		if !app.nav.init {
+			return
+		}
+		if app.nav.midScreen() {
+			app.ui.loadFile(app.nav, true)
+			app.ui.loadFileInfo(app.nav)
+		}
+	case "lo-screen":
+		if !app.nav.init {
+			return
+		}
+		if app.nav.loScreen() {
+			app.ui.loadFile(app.nav, true)
+			app.ui.loadFileInfo(app.nav)
+		}
 	case "toggle":
 		if !app.nav.init {
 			return
diff --git a/lf.1 b/lf.1
index 16ae2d6..487b8fd 100644
--- a/lf.1
+++ b/lf.1
@@ -46,6 +46,9 @@ The following commands are provided by lf:
     jump-prev                (default '[')
     top                      (default 'gg' and '<home>')
     bottom                   (default 'G' and '<end>')
+    hi-screen                (default 'H')
+    mid-screen               (default 'M')
+    lo-screen                (default 'L')
     toggle
     invert                   (default 'v')
     unselect                 (default 'u')
@@ -343,6 +346,14 @@ Change the current working directory to the next/previous jumplist item.
 .PP
 Move the current file selection to the top/bottom of the directory.
 .PP
+.EX
+    hi-screen                (default 'H')
+    mid-screen               (default 'M')
+    lo-screen                (default 'L')
+.EE
+.PP
+Move the current file selection to the top/middle/bottom of the screen.
+.PP
 .EX
     toggle
 .EE
diff --git a/nav.go b/nav.go
index 52a1e40..bb539d2 100644
--- a/nav.go
+++ b/nav.go
@@ -943,6 +943,53 @@ func (nav *nav) bottom() bool {
 	return old != dir.ind
 }
 
+func (nav *nav) hiScreen() bool {
+	dir := nav.currDir()
+
+	old := dir.ind
+	beg := max(dir.ind-dir.pos, 0)
+	offs := gOpts.scrolloff
+	if beg == 0 {
+		offs = 0
+	}
+
+	dir.ind = beg + offs
+	dir.pos = offs
+
+	return old != dir.ind
+}
+
+func (nav *nav) midScreen() bool {
+	dir := nav.currDir()
+
+	old := dir.ind
+	beg := max(dir.ind-dir.pos, 0)
+	end := min(beg+nav.height, len(dir.files))
+
+	half := (end - beg) / 2
+	dir.ind = beg + half
+	dir.pos = half
+
+	return old != dir.ind
+}
+
+func (nav *nav) loScreen() bool {
+	dir := nav.currDir()
+
+	old := dir.ind
+	beg := max(dir.ind-dir.pos, 0)
+	end := min(beg+nav.height, len(dir.files))
+	offs := gOpts.scrolloff
+	if end == len(dir.files) {
+		offs = 0
+	}
+
+	dir.ind = end - 1 - offs
+	dir.pos = end - beg - 1 - offs
+
+	return old != dir.ind
+}
+
 func (nav *nav) toggleSelection(path string) {
 	if _, ok := nav.selections[path]; ok {
 		delete(nav.selections, path)
diff --git a/opts.go b/opts.go
index dae3983..261a235 100644
--- a/opts.go
+++ b/opts.go
@@ -146,6 +146,9 @@ func init() {
 	gOpts.keys["<home>"] = &callExpr{"top", nil, 1}
 	gOpts.keys["G"] = &callExpr{"bottom", nil, 1}
 	gOpts.keys["<end>"] = &callExpr{"bottom", nil, 1}
+	gOpts.keys["H"] = &callExpr{"hi-screen", nil, 1}
+	gOpts.keys["M"] = &callExpr{"mid-screen", nil, 1}
+	gOpts.keys["L"] = &callExpr{"lo-screen", nil, 1}
 	gOpts.keys["["] = &callExpr{"jump-prev", nil, 1}
 	gOpts.keys["]"] = &callExpr{"jump-next", nil, 1}
 	gOpts.keys["<space>"] = &listExpr{[]expr{&callExpr{"toggle", nil, 1}, &callExpr{"down", nil, 1}}, 1}