Add new color scheme and thickness to progress bar

- Rainbow scheme will update bar color based on percentage
starting from .bar--bar.color up to .bar--complete.color in
counterclockwise direction.

- Bar thickness can have 3 styles: thin, normal or thick.

docs/examples/widgets/progress_bar_styled_rainbow.css

@@ -0,0 +1,22 @@
+Bar > .bar--indeterminate {
+    color: $primary;
+    background: $secondary;
+}
+
+Bar > .bar--bar {
+    color: blue;
+    background: $primary 30%;
+}
+
+Bar > .bar--complete {
+    color: red;
+}
+
+PercentageStatus {
+    text-style: reverse;
+    color: $secondary;
+}
+
+ETAStatus {
+    text-style: underline;
+}

docs/examples/widgets/progress_bar_styled_rainbow.py

@@ -0,0 +1,38 @@
+from textual.app import App, ComposeResult
+from textual.containers import Center, Middle
+from textual.timer import Timer
+from textual.widgets import Footer, ProgressBar
+
+
+class StyledExtProgressBar(App[None]):
+    BINDINGS = [
+        ("s", "start", "Start"),
+    ]
+    CSS_PATH = "progress_bar_styled_rainbow.css"
+
+    progress_timer: Timer
+    """Timer to simulate progress happening."""
+
+    def compose(self) -> ComposeResult:
+        with Center():
+            with Middle():
+                yield ProgressBar(color_scheme="rainbow")
+        yield Footer()
+
+    def on_mount(self) -> None:
+        """Set up a timer to simulate progess happening."""
+        self.progress_timer = self.set_interval(1 / 10, self.make_progress, pause=True)
+
+    def make_progress(self) -> None:
+        """Called automatically to advance the progress bar."""
+        self.query_one(ProgressBar).advance(1)
+
+    def action_start(self) -> None:
+        """Start the progress tracking."""
+        self.query_one(ProgressBar).update(total=100)
+        self.progress_timer.resume()
+
+
+if __name__ == "__main__":
+    app = StyledExtProgressBar()
+    app.run()

docs/examples/widgets/progress_bar_styled_rainbow_.py

@@ -0,0 +1,52 @@
+from textual.app import App, ComposeResult
+from textual.containers import Center, Middle
+from textual.timer import Timer
+from textual.widgets import Footer, ProgressBar
+
+
+class StyledExtProgressBar(App[None]):
+    BINDINGS = [
+        ("s", "start", "Start"),
+    ]
+    CSS_PATH = "progress_bar_styled_rainbow.css"
+
+    progress_timer: Timer
+    """Timer to simulate progress happening."""
+
+    def compose(self) -> ComposeResult:
+        with Center():
+            with Middle():
+                yield ProgressBar(color_scheme="rainbow")
+        yield Footer()
+
+    def on_mount(self) -> None:
+        """Set up a timer to simulate progess happening."""
+        self.progress_timer = self.set_interval(1 / 10, self.make_progress, pause=True)
+
+    def make_progress(self) -> None:
+        """Called automatically to advance the progress bar."""
+        self.query_one(ProgressBar).advance(1)
+
+    def action_start(self) -> None:
+        """Start the progress tracking."""
+        self.query_one(ProgressBar).update(total=100)
+        self.progress_timer.resume()
+
+    def key_1(self) -> None:
+        self._action_common_keypress(10)
+
+    def key_5(self) -> None:
+        self._action_common_keypress(50)
+
+    def key_9(self) -> None:
+        self._action_common_keypress(90)
+
+    def _action_common_keypress(self, progress: int) -> None:
+        # Freeze time for the indeterminate progress bar.
+        self.query_one(ProgressBar).query_one("#eta")._get_elapsed_time = lambda: 0
+        self.query_one(ProgressBar).update(total=100, progress=progress)
+        self.progress_timer.pause()
+
+if __name__ == "__main__":
+    app = StyledExtProgressBar()
+    app.run()

docs/examples/widgets/progress_bar_styled_thickness.py

@@ -0,0 +1,38 @@
+from textual.app import App, ComposeResult
+from textual.containers import Center, Middle
+from textual.timer import Timer
+from textual.widgets import Footer, ProgressBar
+
+
+class StyledExtProgressBar(App[None]):
+    BINDINGS = [
+        ("s", "start", "Start"),
+    ]
+    CSS_PATH = "progress_bar_styled.css"
+
+    progress_timer: Timer
+    """Timer to simulate progress happening."""
+
+    def compose(self) -> ComposeResult:
+        with Center():
+            with Middle():
+                yield ProgressBar(thickness=2)
+        yield Footer()
+
+    def on_mount(self) -> None:
+        """Set up a timer to simulate progess happening."""
+        self.progress_timer = self.set_interval(1 / 10, self.make_progress, pause=True)
+
+    def make_progress(self) -> None:
+        """Called automatically to advance the progress bar."""
+        self.query_one(ProgressBar).advance(1)
+
+    def action_start(self) -> None:
+        """Start the progress tracking."""
+        self.query_one(ProgressBar).update(total=100)
+        self.progress_timer.resume()
+
+
+if __name__ == "__main__":
+    app = StyledExtProgressBar()
+    app.run()

docs/examples/widgets/progress_bar_styled_thickness_.py

@@ -0,0 +1,53 @@
+from textual.app import App, ComposeResult
+from textual.containers import Center, Middle
+from textual.timer import Timer
+from textual.widgets import Footer, ProgressBar
+
+
+class StyledExtProgressBar(App[None]):
+    BINDINGS = [
+        ("s", "start", "Start"),
+    ]
+    CSS_PATH = "progress_bar_styled.css"
+
+    progress_timer: Timer
+    """Timer to simulate progress happening."""
+
+    def compose(self) -> ComposeResult:
+        with Center():
+            with Middle():
+                yield ProgressBar()
+        yield Footer()
+
+    def on_mount(self) -> None:
+        """Set up a timer to simulate progess happening."""
+        self.progress_timer = self.set_interval(1 / 10, self.make_progress, pause=True)
+
+    def make_progress(self) -> None:
+        """Called automatically to advance the progress bar."""
+        self.query_one(ProgressBar).advance(1)
+
+    def action_start(self) -> None:
+        """Start the progress tracking."""
+        self.query_one(ProgressBar).update(total=100)
+        self.progress_timer.resume()
+
+    def key_0(self) -> None:
+        self._action_common_keypress(0)
+
+    def key_1(self) -> None:
+        self._action_common_keypress(1)
+
+    def key_2(self) -> None:
+        self._action_common_keypress(2)
+
+    def _action_common_keypress(self, thickness: int) -> None:
+        # Freeze time for the indeterminate progress bar.
+        self.query_one(ProgressBar).query_one("#eta")._get_elapsed_time = lambda: 0
+        self.query_one(ProgressBar).query_one("#bar").thickness = thickness
+        self.query_one(ProgressBar).update(total=100, progress=50)
+        self.progress_timer.pause()
+
+if __name__ == "__main__":
+    app = StyledExtProgressBar()
+    app.run()

docs/widgets/progress_bar.md

@@ -24,7 +24,7 @@ It shows the progress bar in:
 
 === "39% done"
 
-    ```{.textual path="docs/examples/widgets/progress_bar_isolated_.py" press="t"}
+    ```{.textual path="docs/examples/widgets/progress_bar_styled_.py" press="t"}
     ```
 
 === "Completed"
@@ -104,16 +104,79 @@ Refer to the [section below](#styling-the-progress-bar) for more information.
     --8<-- "docs/examples/widgets/progress_bar_styled.tcss"
     ```
 
+### Rainbow Color Schemes
+
+The rainbow color scheme gradually changes the color of the bar as it progresses.
+The initial color is defined by the component class `bar--bar` and the final color by the component class `bar--complete`.
+(The gradient is computed in the HSL color space in the counterclockwise direction.)
+
+=== "Rainbow at 10%"
+
+    ```{.textual path="docs/examples/widgets/progress_bar_styled_rainbow_.py" press="1"}
+    ```
+
+=== "Rainbow at 50%"
+
+    ```{.textual path="docs/examples/widgets/progress_bar_styled_rainbow_.py" press="5"}
+    ```
+
+=== "Rainbow at 90%"
+
+    ```{.textual path="docs/examples/widgets/progress_bar_styled_rainbow_.py" press="9"}
+    ```
+=== "progress_bar_styled_rainbow.py"
+
+    ```python
+    --8<-- "docs/examples/widgets/progress_bar_styled_rainbow.py"
+    ```
+
+=== "progress_bar_styled.css"
+
+    ```sass
+    --8<-- "docs/examples/widgets/progress_bar_styled_rainbow.css"
+    ```
+
+### Progress Bar Thickness Styling
+
+This shows a progress bar with custom bar thickness: thin, normal or thick.
+
+=== "Thin"
+
+    ```{.textual path="docs/examples/widgets/progress_bar_styled_thickness_.py" press="0"}
+    ```
+
+=== "Normal"
+
+    ```{.textual path="docs/examples/widgets/progress_bar_styled_thickness_.py" press="1"}
+    ```
+
+=== "Thick"
+
+    ```{.textual path="docs/examples/widgets/progress_bar_styled_thickness_.py" press="2"}
+    ```
+=== "progress_bar_styled_thickness.py"
+
+    ```python
+    --8<-- "docs/examples/widgets/progress_bar_styled_thickness.py"
+    ```
+
+=== "progress_bar_styled.css"
+
+    ```sass
+    --8<-- "docs/examples/widgets/progress_bar_styled.css"
+    ```
+
 ## Styling the Progress Bar
 
 The progress bar is composed of three sub-widgets that can be styled independently:
 
 | Widget name        | ID            | Description                                                      |
 | ------------------ | ------------- | ---------------------------------------------------------------- |
-| `Bar`              | `#bar`        | The bar that visually represents the progress made.              |
+| `Bar`              | `#bar`        | Bar that visually represents the progress made.              |
 | `PercentageStatus` | `#percentage` | [Label](./label.md) that shows the percentage of completion.     |
 | `ETAStatus`        | `#eta`        | [Label](./label.md) that shows the estimated time to completion. |
 
+
 ### Bar Component Classes
 
 ::: textual.widgets._progress_bar.Bar.COMPONENT_CLASSES
@@ -125,9 +188,9 @@ The progress bar is composed of three sub-widgets that can be styled independent
 
 | Name         | Type    | Default | Description                                                                                             |
 | ------------ | ------- | ------- | ------------------------------------------------------------------------------------------------------- |
-| `percentage` | `float  | None`   | The read-only percentage of progress that has been made. This is `None` if the `total` hasn't been set. |
+| `percentage` | `float` | `None`  | The read-only percentage of progress that has been made. This is `None` if the `total` hasn't been set. |
 | `progress`   | `float` | `0`     | The number of steps of progress already made.                                                           |
-| `total`      | `float  | None`   | The total number of steps that we are keeping track of.                                                 |
+| `total`      | `float` | `None`  | The total number of steps that we are keeping track of.                                                 |
 
 ## Messages
 

src/textual/color.py

@@ -393,9 +393,9 @@ def hsl_blend(
 
         This method calculates a new color on a gradient using the HSL color space.
         The position on the gradient is given by `factor`, which is a float between -1 and 1, where 0 is the original color, and 1 or -1 is the `destination` color.
-        A negative `factor` affects the direction of the hue angle, a positive number is in the clockwise direction, a negative number is in the counter-clockwise direction.
-        For lightess and saturation, only the absolute value of `factor` is used.
-        A value of `gradient` between the two extremes produces a color somewhere between the two end points.
+        The sign of `factor` affects the direction of the hue angle, a positive number is in the clockwise direction, a negative number is in the counter-clockwise direction.
+        For lightness and saturation, only the absolute value of `factor` is used.
+        A value of `factor` between the two extremes produces a color somewhere between the two end points.
 
         Args:
             destination: Another color.
@@ -405,10 +405,10 @@ def hsl_blend(
         Returns:
             A new color.
         """
-        abs_factor = factor if factor >= 0 else -1.0 * factor
+        abs_factor = abs(factor)
         if factor == 0:
             return self
-        elif factor >= 1 or factor <= -1:
+        elif abs_factor >= 1:
             return destination
 
         hsl_1 = self.hsl
@@ -421,19 +421,11 @@ def hsl_blend(
         else:
             new_alpha = alpha
 
-        # When the factor is > 0, hue is clockwise, otherwise it is counter-clockwise.
-        if factor > 0:
-            if hsl_1.h <= hsl_2.h:
-                new_h = hsl_1.h + (hsl_2.h - hsl_1.h) * abs_factor
-            else:
-                new_h = hsl_1.h + (hsl_2.h + 1.0 - hsl_1.h) * abs_factor
-                new_h = new_h - 1.0 if new_h >= 1.0 else new_h
+        sign = 1 if factor > 0 else -1
+        if (sign * hsl_1.h) <= (sign * hsl_2.h):
+            new_h = hsl_1.h + (hsl_2.h - hsl_1.h) * abs_factor
         else:
-            if hsl_1.h >= hsl_2.h:
-                new_h = hsl_1.h + (hsl_2.h - hsl_1.h) * abs_factor
-            else:
-                new_h = (hsl_1.h + (hsl_2.h - 1.0 - hsl_1.h) * abs_factor)
-                new_h = new_h + 1.0 if new_h < 0.0 else new_h
+            new_h = (hsl_1.h + (hsl_2.h + sign - hsl_1.h) * abs_factor) % 1
 
         new_s = hsl_1.s + (hsl_2.s - hsl_1.s) * abs_factor
         new_l = hsl_1.l + (hsl_2.l - hsl_1.l) * abs_factor