From 939da082b2f5d09fd9b8997114aafa53f597a3a7 Mon Sep 17 00:00:00 2001
From: qraqras <q100rrraaa@gmail.com>
Date: Sat, 28 Jun 2025 08:18:19 +0000
Subject: [PATCH 1/4] Fix 6633

---
 packages/mermaid/src/diagrams/block/layout.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/packages/mermaid/src/diagrams/block/layout.ts b/packages/mermaid/src/diagrams/block/layout.ts
index a00e935ac..9daf0b4c1 100644
--- a/packages/mermaid/src/diagrams/block/layout.ts
+++ b/packages/mermaid/src/diagrams/block/layout.ts
@@ -270,7 +270,11 @@ function layoutBlocks(block: Block, db: BlockDB) {
       if (child.children) {
         layoutBlocks(child, db);
       }
-      columnPos += child?.widthInColumns ?? 1;
+      let columnsFilled = child?.widthInColumns ?? 1;
+      if (columns > 0) {
+        columnsFilled = Math.min(columnsFilled, columns - (columnPos % columns));
+      }
+      columnPos += columnsFilled;
       log.debug('abc88 columnsPos', child, columnPos);
     }
   }

From e073c80019982407bff45f3d5f68a78c0a0a4afa Mon Sep 17 00:00:00 2001
From: Alois Klink <alois@aloisklink.com>
Date: Tue, 29 Jul 2025 15:27:10 +0900
Subject: [PATCH 2/4] test(e2e): test block column overflowing

Add a test-case for 939da082b (Fix 6633, 2025-06-28), that checks
whether overflowing blocks render correctly.
---
 cypress/integration/rendering/block.spec.js | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/cypress/integration/rendering/block.spec.js b/cypress/integration/rendering/block.spec.js
index 589a30fde..f01d59375 100644
--- a/cypress/integration/rendering/block.spec.js
+++ b/cypress/integration/rendering/block.spec.js
@@ -384,4 +384,17 @@ describe('Block diagram', () => {
       {}
     );
   });
+
+  it('BL30: block should overflow if too wide for columns', () => {
+    imgSnapshotTest(
+      `block-beta
+  columns 2
+  fit:2
+  overflow:3
+  short:1
+  also_overflow:2
+`,
+      {}
+    );
+  });
 });

From 8bb29fc879329ad109898e4025b4f4eba2ab0649 Mon Sep 17 00:00:00 2001
From: Alois Klink <alois@aloisklink.com>
Date: Tue, 29 Jul 2025 15:31:58 +0900
Subject: [PATCH 3/4] docs(block): add changeset for overflow bug

Add a changeset that explains that overflowing blocks no longer
create an empty line in block diagrams or cause bugs in later lines.

Technically, this is a breaking change since it can change the layout of
block diagrams, but this diagram is still in `-beta` and they all will
still render correctly.
---
 .changeset/lovely-queens-own.md | 8 ++++++++
 1 file changed, 8 insertions(+)
 create mode 100644 .changeset/lovely-queens-own.md

diff --git a/.changeset/lovely-queens-own.md b/.changeset/lovely-queens-own.md
new file mode 100644
index 000000000..edc8dda2d
--- /dev/null
+++ b/.changeset/lovely-queens-own.md
@@ -0,0 +1,8 @@
+---
+'mermaid': patch
+---
+
+fix(block): overflowing blocks no longer affect later lines
+
+This may change the layout of block diagrams that have overflowing lines
+(i.e. block diagrams that use up more columns that the `columns` specifier).

From b7a591b8d3ddb0867036ea87b5d7bd4523ff047f Mon Sep 17 00:00:00 2001
From: Alois Klink <alois@aloisklink.com>
Date: Tue, 29 Jul 2025 15:45:06 +0900
Subject: [PATCH 4/4] docs(block): add clarifying comment for overflow

This line is a bit confusing to me, so I thought I should clarify it!

See: 939da082b2f5d09fd9b8997114aafa53f597a3a7
---
 packages/mermaid/src/diagrams/block/layout.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/packages/mermaid/src/diagrams/block/layout.ts b/packages/mermaid/src/diagrams/block/layout.ts
index 9daf0b4c1..ea0de6312 100644
--- a/packages/mermaid/src/diagrams/block/layout.ts
+++ b/packages/mermaid/src/diagrams/block/layout.ts
@@ -272,6 +272,7 @@ function layoutBlocks(block: Block, db: BlockDB) {
       }
       let columnsFilled = child?.widthInColumns ?? 1;
       if (columns > 0) {
+        // Make sure overflowing lines do not affect later lines
         columnsFilled = Math.min(columnsFilled, columns - (columnPos % columns));
       }
       columnPos += columnsFilled;