Render height fix (#2246)

* Fix issue where height - totalvpad < 0 would cause render_lines crash

* Update changelog

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - Change SVG export to create a simpler SVG
+- Fix render_lines crash when render height was negative https://github.com/Textualize/rich/pull/2246
 
 ## [12.3.0] - 2022-04-26
 

rich/console.py

@@ -1327,6 +1327,11 @@ def render_lines(
             _rendered = self.render(renderable, render_options)
             if style:
                 _rendered = Segment.apply_style(_rendered, style)
+
+            render_height = render_options.height
+            if render_height is not None:
+                render_height = max(0, render_height)
+
             lines = list(
                 islice(
                     Segment.split_and_crop_lines(
@@ -1336,7 +1341,7 @@ def render_lines(
                         pad=pad,
                     ),
                     None,
-                    render_options.height,
+                    render_height,
                 )
             )
             if render_options.height is not None:

tests/test_console.py

@@ -20,6 +20,7 @@
 )
 from rich.control import Control
 from rich.measure import measure_renderables
+from rich.padding import Padding
 from rich.pager import SystemPager
 from rich.panel import Panel
 from rich.region import Region
@@ -862,3 +863,18 @@ def __rich_console__(self, console, options):
     expected = "╭──────────────────╮\n│ ╭──────────────╮ │\n│ │ foo          │ │\n│ ╰──────────────╯ │\n│ ╭──────────────╮ │\n│ │ bar          │ │\n│ ╰──────────────╯ │\n│                  │\n│                  │\n│                  │\n│                  │\n╰──────────────────╯\n"
 
     assert result == expected
+
+
+def test_render_lines_height_minus_vertical_pad_is_negative():
+    # https://github.com/Textualize/textual/issues/389
+    console = Console(
+        force_terminal=True,
+        color_system="truecolor",
+        width=20,
+        height=40,
+        legacy_windows=False,
+    )
+    options = console.options.update_height(1)
+
+    # Ensuring that no exception is raised...
+    console.render_lines(Padding("hello", pad=(1, 0)), options=options)