Add gap param to st.columns

e2e/scripts/st_columns.py

@@ -29,3 +29,19 @@
 # Variable-width columns
 for c in st.columns((1, 2, 3, 4)):
     c.image(CAT_IMAGE)
+
+# Various column gaps
+c4, c5, c6 = st.columns(3, gap="small")
+c4.image(CAT_IMAGE)
+c5.image(CAT_IMAGE)
+c6.image(CAT_IMAGE)
+
+c7, c8, c9 = st.columns(3, gap="medium")
+c7.image(CAT_IMAGE)
+c8.image(CAT_IMAGE)
+c9.image(CAT_IMAGE)
+
+c10, c11, c12 = st.columns(3, gap="large")
+c10.image(CAT_IMAGE)
+c11.image(CAT_IMAGE)
+c12.image(CAT_IMAGE)

e2e/specs/st_columns.spec.js

@@ -61,7 +61,7 @@ describe("st.column", () => {
     // This assertion ensures that the report rerun completes first
     cy.get("[data-testid='stHorizontalBlock'] [data-testid='column']").should(
       "have.length",
-      7
+      16
     );
 
     // When layout was shifting, there was an old "flex: 8" block here.
@@ -70,4 +70,20 @@ describe("st.column", () => {
       3
     ).should("have.css", "flex", "1 1 calc(10% - 16px)");
   });
+
+  it("creates small gap between columns", () => {
+    cy.getIndexed("[data-testid='stHorizontalBlock']",
+    2).matchThemedSnapshots("columns-small-gap");
+  });
+
+  it("creates medium gap between columns", () => {
+    cy.getIndexed("[data-testid='stHorizontalBlock']",
+    3).matchThemedSnapshots("columns-medium-gap");
+  });
+
+  it("creates large gap between columns", () => {
+    cy.getIndexed("[data-testid='stHorizontalBlock']",
+    4).matchThemedSnapshots("columns-large-gap");
+  });
+
 });

frontend/src/components/core/Block/Block.test.tsx

@@ -35,7 +35,7 @@ function makeHorizontalBlock(numColumns: number): BlockNode {
 
   return new BlockNode(
     Array.from({ length: numColumns }, () => makeColumn(weight)),
-    new BlockProto({ allowEmpty: true, horizontal: true })
+    new BlockProto({ allowEmpty: true, horizontal: { gap: "small" } })
   )
 }
 

frontend/src/components/core/Block/Block.tsx

@@ -105,6 +105,7 @@ const BlockNodeRenderer = (props: BlockPropsWithWidth): ReactElement => {
     return (
       <StyledColumn
         weight={node.deltaBlock.column.weight ?? 0}
+        gap={node.deltaBlock.column.gap ?? ""}
         data-testid="column"
       >
         {child}
@@ -173,8 +174,10 @@ const HorizontalBlock = (props: BlockPropsWithWidth): ReactElement => {
   // Create a horizontal block as the parent for columns.
   // The children are always columns, but this is not checked. We just trust the Python side to
   // do the right thing, then we ask ChildRenderer to handle it.
+  const gap = props.node.deltaBlock.horizontal?.gap ?? ""
+
   return (
-    <StyledHorizontalBlock data-testid="stHorizontalBlock">
+    <StyledHorizontalBlock gap={gap} data-testid="stHorizontalBlock">
       <ChildRenderer {...props} />
     </StyledHorizontalBlock>
   )

frontend/src/components/core/Block/styled-components.ts

@@ -19,16 +19,35 @@ import React from "react"
 import styled from "@emotion/styled"
 import { Theme } from "src/theme"
 
-export const StyledHorizontalBlock = styled.div(({ theme }) => ({
-  // While using flex for columns, padding is used for large screens and gap
-  // for small ones. This can be adjusted once more information is passed.
-  // More information and discussions can be found: Issue #2716, PR #2811
-  display: "flex",
-  flexWrap: "wrap",
-  flexGrow: 1,
-  alignItems: "stretch",
-  gap: theme.spacing.lg,
-}))
+function translateGapWidth(gap: string, theme: Theme): string {
+  let gapWidth = theme.spacing.lg
+  if (gap === "medium") {
+    gapWidth = theme.spacing.threeXL
+  } else if (gap === "large") {
+    gapWidth = theme.spacing.fourXL
+  }
+  return gapWidth
+}
+export interface StyledHorizontalBlockProps {
+  gap: string
+}
+
+export const StyledHorizontalBlock = styled.div<StyledHorizontalBlockProps>(
+  ({ theme, gap }) => {
+    const gapWidth = translateGapWidth(gap, theme)
+
+    return {
+      // While using flex for columns, padding is used for large screens and gap
+      // for small ones. This can be adjusted once more information is passed.
+      // More information and discussions can be found: Issue #2716, PR #2811
+      display: "flex",
+      flexWrap: "wrap",
+      flexGrow: 1,
+      alignItems: "stretch",
+      gap: gapWidth,
+    }
+  }
+)
 
 export interface StyledElementContainerProps {
   isStale: boolean
@@ -74,12 +93,14 @@ export const StyledElementContainer = styled.div<StyledElementContainerProps>(
 
 interface StyledColumnProps {
   weight: number
+  gap: string
 }
 
 export const StyledColumn = styled.div<StyledColumnProps>(
-  ({ weight, theme }) => {
+  ({ weight, gap, theme }) => {
     const percentage = weight * 100
-    const width = `calc(${percentage}% - ${theme.spacing.lg})`
+    const gapWidth = translateGapWidth(gap, theme)
+    const width = `calc(${percentage}% - ${gapWidth})`
 
     return {
       // Calculate width based on percentage, but fill all available space,

frontend/src/components/core/StatusWidget/__snapshots__/StatusWidget.test.tsx.snap

@@ -383,6 +383,7 @@ exports[`Tooltip element renders running img correctly with custom dark backgrou
         "sidebarTopSpace": "6rem",
       },
       "spacing": Object {
+        "fourXL": "4rem",
         "halfSmFont": "7px",
         "lg": "1rem",
         "md": "0.75rem",
@@ -795,6 +796,7 @@ exports[`Tooltip element renders running img correctly with custom dark backgrou
           "sidebarTopSpace": "6rem",
         },
         "spacing": Object {
+          "fourXL": "4rem",
           "halfSmFont": "7px",
           "lg": "1rem",
           "md": "0.75rem",
@@ -3554,6 +3556,7 @@ exports[`Tooltip element renders running img correctly with custom light backgro
         "sidebarTopSpace": "6rem",
       },
       "spacing": Object {
+        "fourXL": "4rem",
         "halfSmFont": "7px",
         "lg": "1rem",
         "md": "0.75rem",
@@ -3966,6 +3969,7 @@ exports[`Tooltip element renders running img correctly with custom light backgro
           "sidebarTopSpace": "6rem",
         },
         "spacing": Object {
+          "fourXL": "4rem",
           "halfSmFont": "7px",
           "lg": "1rem",
           "md": "0.75rem",
@@ -6725,6 +6729,7 @@ exports[`Tooltip element renders running img correctly with darkTheme 1`] = `
         "sidebarTopSpace": "6rem",
       },
       "spacing": Object {
+        "fourXL": "4rem",
         "halfSmFont": "7px",
         "lg": "1rem",
         "md": "0.75rem",
@@ -7137,6 +7142,7 @@ exports[`Tooltip element renders running img correctly with darkTheme 1`] = `
           "sidebarTopSpace": "6rem",
         },
         "spacing": Object {
+          "fourXL": "4rem",
           "halfSmFont": "7px",
           "lg": "1rem",
           "md": "0.75rem",
@@ -9896,6 +9902,7 @@ exports[`Tooltip element renders running img correctly with lightTheme 1`] = `
         "sidebarTopSpace": "6rem",
       },
       "spacing": Object {
+        "fourXL": "4rem",
         "halfSmFont": "7px",
         "lg": "1rem",
         "md": "0.75rem",
@@ -10308,6 +10315,7 @@ exports[`Tooltip element renders running img correctly with lightTheme 1`] = `
           "sidebarTopSpace": "6rem",
         },
         "spacing": Object {
+          "fourXL": "4rem",
           "halfSmFont": "7px",
           "lg": "1rem",
           "md": "0.75rem",

frontend/src/theme/primitives/spacing.ts

@@ -30,4 +30,5 @@ export const spacing = {
   xl: "1.25rem",
   twoXL: "1.5rem",
   threeXL: "2rem",
+  fourXL: "4rem",
 }

lib/streamlit/elements/layouts.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import cast, List, Sequence, TYPE_CHECKING, Union
+from typing import cast, List, Sequence, TYPE_CHECKING, Union, Optional
 
 from streamlit.beta_util import function_beta_warning
 from streamlit.errors import StreamlitAPIException
@@ -69,7 +69,9 @@ def container(self) -> "DeltaGenerator":
         return self.dg._block()
 
     # TODO: Enforce that columns are not nested or in Sidebar
-    def columns(self, spec: SpecType) -> List["DeltaGenerator"]:
+    def columns(
+        self, spec: SpecType, *, gap: Optional[str] = "small"
+    ) -> List["DeltaGenerator"]:
         """Insert containers laid out as side-by-side columns.
 
         Inserts a number of multi-element containers laid out side-by-side and
@@ -97,6 +99,10 @@ def columns(self, spec: SpecType) -> List["DeltaGenerator"]:
                 For example, `st.columns([3, 1, 2])` creates 3 columns where
                 the first column is 3 times the width of the second, and the last
                 column is 2 times that width.
+        gap : string ("small", "medium", or "large")
+            An optional string, which indicates the size of the gap between each column.
+            The default is a small gap between columns. This argument can only be supplied by
+            keyword.
 
         Returns
         -------
@@ -159,14 +165,30 @@ def columns(self, spec: SpecType) -> List["DeltaGenerator"]:
         if len(weights) == 0 or any(weight <= 0 for weight in weights):
             raise weights_exception
 
+        def column_gap(gap):
+            if type(gap) == str:
+                gap_size = gap.lower()
+                valid_sizes = ["small", "medium", "large"]
+
+                if gap_size in valid_sizes:
+                    return gap_size
+
+            raise StreamlitAPIException(
+                'The gap argument to st.columns must be "small", "medium", or "large". \n'
+                f"The argument passed was {gap}."
+            )
+
+        gap_size = column_gap(gap)
+
         def column_proto(normalized_weight: float) -> BlockProto:
             col_proto = BlockProto()
             col_proto.column.weight = normalized_weight
+            col_proto.column.gap = gap_size
             col_proto.allow_empty = True
             return col_proto
 
         block_proto = BlockProto()
-        block_proto.horizontal.SetInParent()
+        block_proto.horizontal.gap = gap_size
         row = self.dg._block(block_proto)
         total_weight = sum(weights)
         return [row._block(column_proto(w / total_weight)) for w in weights]

lib/tests/streamlit/layouts_test.py

@@ -66,6 +66,57 @@ def test_not_equal_width_float_columns(self):
         self.assertEqual(columns_blocks[1].add_block.column.weight, 2.5 / sum_weights)
         self.assertEqual(columns_blocks[2].add_block.column.weight, 5.0 / sum_weights)
 
+    def test_columns_with_default_small_gap(self):
+        """Test that it works correctly with no gap argument (gap size is default of small)"""
+
+        columns = st.columns(3)
+
+        all_deltas = self.get_all_deltas_from_queue()
+
+        horizontal_block = all_deltas[0]
+        columns_blocks = all_deltas[1:4]
+
+        # 4 elements will be created: 1 horizontal block, 3 columns, each receives "small" gap arg
+        self.assertEqual(len(all_deltas), 4)
+        self.assertEqual(horizontal_block.add_block.horizontal.gap, "small")
+        self.assertEqual(columns_blocks[0].add_block.column.gap, "small")
+        self.assertEqual(columns_blocks[1].add_block.column.gap, "small")
+        self.assertEqual(columns_blocks[2].add_block.column.gap, "small")
+
+    def test_columns_with_medium_gap(self):
+        """Test that it works correctly with "medium" gap argument"""
+
+        columns = st.columns(3, gap="medium")
+
+        all_deltas = self.get_all_deltas_from_queue()
+
+        horizontal_block = all_deltas[0]
+        columns_blocks = all_deltas[1:4]
+
+        # 4 elements will be created: 1 horizontal block, 3 columns, each receives "medium" gap arg
+        self.assertEqual(len(all_deltas), 4)
+        self.assertEqual(horizontal_block.add_block.horizontal.gap, "medium")
+        self.assertEqual(columns_blocks[0].add_block.column.gap, "medium")
+        self.assertEqual(columns_blocks[1].add_block.column.gap, "medium")
+        self.assertEqual(columns_blocks[2].add_block.column.gap, "medium")
+
+    def test_columns_with_large_gap(self):
+        """Test that it works correctly with "large" gap argument"""
+
+        columns = st.columns(3, gap="LARGE")
+
+        all_deltas = self.get_all_deltas_from_queue()
+
+        horizontal_block = all_deltas[0]
+        columns_blocks = all_deltas[1:4]
+
+        # 4 elements will be created: 1 horizontal block, 3 columns, each receives "large" gap arg
+        self.assertEqual(len(all_deltas), 4)
+        self.assertEqual(horizontal_block.add_block.horizontal.gap, "large")
+        self.assertEqual(columns_blocks[0].add_block.column.gap, "large")
+        self.assertEqual(columns_blocks[1].add_block.column.gap, "large")
+        self.assertEqual(columns_blocks[2].add_block.column.gap, "large")
+
 
 class ExpanderTest(testutil.DeltaGeneratorTestCase):
     def test_label_required(self):

proto/streamlit/proto/Block.proto

@@ -31,10 +31,12 @@ message Block {
   }
 
   message Horizontal {
+    string gap = 1;
   }
 
   message Column {
     double weight = 1;
+    string gap = 2;
   }
 
   message Expandable {