Add support for negative --height

  fzf --height=-1

Close #3487

5 files changed, 44 insertions, 9 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 378238d6..fec32d97 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,8 +1,14 @@
 CHANGELOG
 =========
 
-0.44.2
+0.45.0
 ------
+- Added support for negative height
+  ```sh
+  # Terminal height minus 1, so you can still see the command line
+  fzf --height=-1
+  ```
+  - This handles a terminal resize better than `--height=$(($(tput lines) - 1))`
 - Added `accept-or-print-query` action that acts like `accept` but prints the
   current query when there's no match for the query
   ```sh
diff --git a/man/man1/fzf.1 b/man/man1/fzf.1
index 0205d0ad..c4fe788c 100644
--- a/man/man1/fzf.1
+++ b/man/man1/fzf.1
@@ -21,7 +21,7 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ..
-.TH fzf 1 "Nov 2023" "fzf 0.44.1" "fzf - a command-line fuzzy finder"
+.TH fzf 1 "Dec 2023" "fzf 0.45.0" "fzf - a command-line fuzzy finder"
 
 .SH NAME
 fzf - a command-line fuzzy finder
@@ -192,9 +192,21 @@ Label characters for \fBjump\fR and \fBjump-accept\fR
 .TP
 .BI "--height=" "[~]HEIGHT[%]"
 Display fzf window below the cursor with the given height instead of using
-the full screen. When prefixed with \fB~\fR, fzf will automatically determine
-the height in the range according to the input size. Note that adaptive height
-is not compatible with top/bottom margin and padding given in percent size.
+the full screen.
+
+If a negative value is specified, the height is calculated as the terminal
+height minus the given value.
+
+  fzf --height=-1
+
+When prefixed with \fB~\fR, fzf will automatically determine the height in the
+range according to the input size. Note that adaptive height is not compatible
+with top/bottom margin and padding given in percent size. It is also not
+compatible with a negative height value.
+
+  # Will not take up 100% of the screen
+  seq 5 | fzf --height=~100%
+
 .TP
 .BI "--min-height=" "HEIGHT"
 Minimum height when \fB--height\fR is given in percent (default: 10).
diff --git a/src/core.go b/src/core.go
index e21e8c0a..ed56a879 100644
--- a/src/core.go
+++ b/src/core.go
@@ -200,7 +200,7 @@ func Run(opts *Options, version string, revision string) {
 	padHeight := 0
 	heightUnknown := opts.Height.auto
 	if heightUnknown {
-		maxFit, padHeight = terminal.MaxFitAndPad(opts)
+		maxFit, padHeight = terminal.MaxFitAndPad()
 	}
 	deferred := opts.Select1 || opts.Exit0
 	go terminal.Loop()
diff --git a/src/options.go b/src/options.go
index 57f2f1e1..ca8b2476 100644
--- a/src/options.go
+++ b/src/options.go
@@ -57,6 +57,8 @@ const usage = `usage: fzf [options]
   Layout
     --height=[~]HEIGHT[%]  Display fzf window below the cursor with the given
                            height instead of using fullscreen.
+                           A negative value is calcalated as the terminal height
+                           minus the given value.
                            If prefixed with '~', fzf will determine the height
                            according to the input size.
     --min-height=HEIGHT    Minimum height when --height is given in percent
@@ -157,6 +159,7 @@ type heightSpec struct {
 	size    float64
 	percent bool
 	auto    bool
+	inverse bool
 }
 
 type sizeSpec struct {
@@ -1386,6 +1389,13 @@ func parseHeight(str string) heightSpec {
 		heightSpec.auto = true
 		str = str[1:]
 	}
+	if strings.HasPrefix(str, "-") {
+		if heightSpec.auto {
+			errorExit("negative(-) height is not compatible with adaptive(~) height")
+		}
+		heightSpec.inverse = true
+		str = str[1:]
+	}
 
 	size := parseSize(str, 100, "height")
 	heightSpec.size = size.size
diff --git a/src/terminal.go b/src/terminal.go
index 4a4498bb..394be4fc 100644
--- a/src/terminal.go
+++ b/src/terminal.go
@@ -594,10 +594,17 @@ func makeSpinner(unicode bool) []string {
 }
 
 func evaluateHeight(opts *Options, termHeight int) int {
+	size := opts.Height.size
 	if opts.Height.percent {
-		return util.Max(int(opts.Height.size*float64(termHeight)/100.0), opts.MinHeight)
+		if opts.Height.inverse {
+			size = 100 - size
+		}
+		return util.Max(int(size*float64(termHeight)/100.0), opts.MinHeight)
+	}
+	if opts.Height.inverse {
+		size = float64(termHeight) - size
 	}
-	return int(opts.Height.size)
+	return int(size)
 }
 
 // NewTerminal returns new Terminal object
@@ -819,7 +826,7 @@ func (t *Terminal) extraLines() int {
 	return extra
 }
 
-func (t *Terminal) MaxFitAndPad(opts *Options) (int, int) {
+func (t *Terminal) MaxFitAndPad() (int, int) {
 	_, screenHeight, marginInt, paddingInt := t.adjustMarginAndPadding()
 	padHeight := marginInt[0] + marginInt[2] + paddingInt[0] + paddingInt[2]
 	fit := screenHeight - padHeight - t.extraLines()