Added input mode for section header number

Added section-header-num to help-key and help options.
README.md has also been updated, as it has been added to the help.
Improved comments.

README.md

@@ -371,10 +371,14 @@ ov --section-delimiter "^#" --section-header README.md
 
 It is also useful as a pager for `git``.
 
+The number of lines in section-header can be changed.
+
+You can specify the number of lines using the `--section-header-num` option or key input(default key `F7`).
+
 ```gitconfig
 [pager]
 	diff = "ov -F --section-delimiter '^diff' --section-header"
-	log = "ov -F --section-delimiter '^commit' --section-header"
+  log = "ov -F --section-delimiter '^commit' --section-header --section-header-num 3"
 ```
 
 ###  3.10. <a name='follow-mode'></a>Follow mode
@@ -721,6 +725,7 @@ MemoryLimit: 1000
 | -H,   | --header int                               | number of header lines to be displayed constantly              |
 | -h,   | --help                                     | help for ov                                                    |
 |       | --help-key                                 | display key bind information                                   |
+|       | --hscroll-width [int\|int%\|.int]          | width to scroll horizontally [int\|int%\|.int] (default "10%") |
 |       | --incsearch[=true\|false]                  | incremental search (default true)                              |
 | -j,   | --jump-target [int\|int%\|.int\|'section'] | jump target [int\|int%\|.int\|'section']                       |
 | -n,   | --line-number                              | line number mode                                               |
@@ -733,6 +738,7 @@ MemoryLimit: 1000
 |       | --regexp-search                            | regular expression search                                      |
 |       | --section-delimiter regexp                 | regexp for section delimiter .e.g. "^#"                        |
 |       | --section-header                           | enable section-delimiter line as Header                        |
+|       | --section-header-num int                   | number of header lines (default 1)                             |
 |       | --section-start int                        | section start position                                         |
 |       | --skip-extract                             | skip extracting compressed files                               |
 |       | --skip-lines int                           | skip the number of lines                                       |
@@ -774,6 +780,8 @@ It can also be changed after startup.
 | [right]                       | * scroll to right                                  |
 | [ctrl+left]                   | * scroll left half screen                          |
 | [ctrl+right]                  | * scroll right half screen                         |
+| [ctrl+shift+left]             | * scroll left specified width                      |
+| [ctrl+shift+right]            | * scroll right specified width                     |
 | [shift+Home]                  | * go to beginning of line                          |
 | [shift+End]                   | * go to end of line                                |
 | [g]                           | * go to line(input number or `.n` or `n%` allowed) |
@@ -815,6 +823,7 @@ It can also be changed after startup.
 | [^]                           | * previous section                                 |
 | [9]                           | * last section                                     |
 | [F2]                          | * follow section mode toggle                       |
+| [F7]                          | * section header number                            |
 | **Close and reload**          |                                                    |
 | [ctrl+F9], [ctrl+alt+s]       | * close file                                       |
 | [ctrl+alt+l], [F5]            | * reload file                                      |

oviewer/action.go

@@ -321,6 +321,24 @@ func (root *Root) setSkipLines(input string) {
 	root.setMessagef("Set skip lines %d", num)
 }
 
+func (root *Root) setSectionNum(input string) {
+	num, err := strconv.Atoi(input)
+	if err != nil {
+		root.setMessagef("Set section header num: %s", ErrInvalidNumber.Error())
+		return
+	}
+	if num < 0 {
+		root.setMessagef("Set section header num: %s", ErrOutOfRange.Error())
+		return
+	}
+	if root.Doc.SectionHeaderNum == num {
+		return
+	}
+
+	root.Doc.SectionHeaderNum = num
+	root.setMessagef("Set section header num %d", num)
+}
+
 // suspend suspends the current screen display and runs the shell.
 // It will return when you exit the shell.
 func (root *Root) suspend() {

oviewer/draw.go

@@ -120,7 +120,7 @@ func (root *Root) drawSectionHeader(lN int) int {
 	}
 
 	pn := lN
-	// If the line number is 0, it is the first line.
+	// prevSection searches for the section above the specified line.
 	if pn == 0 {
 		pn = 1
 	}

oviewer/event.go

@@ -84,6 +84,8 @@ func (root *Root) eventLoop(ctx context.Context, quitChan chan<- struct{}) {
 			root.setJumpTarget(ev.value)
 		case *eventSaveBuffer:
 			root.saveBuffer(ev.value)
+		case *eventSectionNum:
+			root.setSectionNum(ev.value)
 
 		// tcell events
 		case *tcell.EventResize:

oviewer/input.go

@@ -29,6 +29,7 @@ const (
 	MultiColor                 // MultiColor is multi-word coloring.
 	JumpTarget                 // JumpTarget is the position to display the search results.
 	SaveBuffer                 // SaveBuffer is the save buffer.
+	SectionNum                 // SectionNum is the section number.
 )
 
 // Input represents the status of various inputs.

oviewer/input_section_num.go

@@ -0,0 +1,61 @@
+package oviewer
+
+import (
+	"strconv"
+
+	"github.com/gdamore/tcell/v2"
+)
+
+// setSectionNumMode sets the inputMode to SectionNum.
+func (root *Root) setSectionNumMode() {
+	input := root.input
+	input.value = ""
+	input.cursorX = 0
+	input.Event = newSectionNumEvent()
+}
+
+// eventSectionNum represents the section num input mode.
+type eventSectionNum struct {
+	tcell.EventTime
+	value string
+}
+
+// newSectionNumEvent returns Event.
+func newSectionNumEvent() *eventSectionNum {
+	return &eventSectionNum{}
+}
+
+// Mode returns InputMode.
+func (e *eventSectionNum) Mode() InputMode {
+	return SectionNum
+}
+
+// Prompt returns the prompt string in the input field.
+func (e *eventSectionNum) Prompt() string {
+	return "Section Num:"
+}
+
+// Confirm returns the event when the input is confirmed.
+func (e *eventSectionNum) Confirm(str string) tcell.Event {
+	e.value = str
+	e.SetEventNow()
+	return e
+}
+
+// Up returns strings when the up key is pressed during input.
+func (e *eventSectionNum) Up(str string) string {
+	n, err := strconv.Atoi(str)
+	if err != nil {
+		return "0"
+	}
+	return strconv.Itoa(n + 1)
+}
+
+// Down returns strings when the down key is pressed during input.
+func (e *eventSectionNum) Down(str string) string {
+	n, err := strconv.Atoi(str)
+	if err != nil || n <= 0 {
+		return "0"
+	}
+	return strconv.Itoa(n - 1)
+}

oviewer/input_skip.go

@@ -14,7 +14,7 @@ func (root *Root) setSkipLinesMode() {
 	input.Event = newSkipLinesEvent()
 }
 
-// eventSkipLines represents the goto input mode.
+// eventSkipLines represents the skip lines input mode.
 type eventSkipLines struct {
 	tcell.EventTime
 	value string

oviewer/input_viewmode.go

@@ -19,7 +19,7 @@ func viewModeCandidate() *candidate {
 	}
 }
 
-// eventViewMode represents the mode input mode.
+// eventViewMode represents the view mode input mode.
 type eventViewMode struct {
 	tcell.EventTime
 	clist *candidate

oviewer/keybind.go

@@ -68,6 +68,7 @@ const (
 	actionSkipLines      = "skip_lines"
 	actionTabWidth       = "tabwidth"
 	actionGoLine         = "goto"
+	actionSectionNum     = "section_num"
 	actionNextSearch     = "next_search"
 	actionNextBackSearch = "next_backsearch"
 	actionNextDoc        = "next_doc"
@@ -147,6 +148,7 @@ func (root *Root) handlers() map[string]func() {
 		actionSkipLines:      root.setSkipLinesMode,
 		actionTabWidth:       root.setTabWidthMode,
 		actionGoLine:         root.setGoLineMode,
+		actionSectionNum:     root.setSectionNumMode,
 		actionNextSearch:     root.sendNextSearch,
 		actionNextBackSearch: root.sendNextBackSearch,
 		actionNextDoc:        root.nextDoc,
@@ -229,6 +231,7 @@ func defaultKeyBinds() KeyBind {
 		actionSkipLines:      {"ctrl+s"},
 		actionTabWidth:       {"t"},
 		actionGoLine:         {"g"},
+		actionSectionNum:     {"F7"},
 		actionNextSearch:     {"n"},
 		actionNextBackSearch: {"N"},
 		actionNextDoc:        {"]"},
@@ -338,6 +341,7 @@ func (k KeyBind) String() string {
 	k.writeKeyBind(&b, actionPrevSection, "previous section")
 	k.writeKeyBind(&b, actionLastSection, "last section")
 	k.writeKeyBind(&b, actionFollowSection, "follow section mode toggle")
+	k.writeKeyBind(&b, actionSectionNum, "section header number")
 
 	fmt.Fprint(&b, "\n\tClose and reload\n")
 	fmt.Fprint(&b, "\n")