From 3ff304014b72f767ee72b85d162b2445bd8ba2c8 Mon Sep 17 00:00:00 2001
From: Lephenixnoir <sebastien.mld@numericable.fr>
Date: Mon, 17 Jun 2019 21:41:50 -0400
Subject: [PATCH] README update for matrices

---
 README.md | 14 +++++++-------
 src/env.c |  4 +++-
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/README.md b/README.md
index 997e1c9..78cf152 100644
--- a/README.md
+++ b/README.md
@@ -3,16 +3,17 @@
 This library is a customizable 2D math rendering tool for calculators. It can be used to render 2D formulae, either from an existing structure or TeX syntax.
 
 ```latex
-\frac{x^7\left[X,Y\right]+3\left|\frac{A}{B}\right>}
-     {\left\{\frac{a_k+b_k}{5!}\right\}^n}
-+ \sum_{k=1}^nk(-1)^k
+\frac{x^7 \left[X,Y\right] + 3\left|\frac{A}{B}\right>}
+     {\left\{\frac{a_k+b_k}{k!}\right\}^5}
++ \int_a^b \frac{\left(b-t\right)^{n+1}}{n!} dt
++ \left(\begin{matrix} \frac{1}{2} & 5 \\ -1 & a+b \end{matrix}\right)
 ```
 
-![Sample image](https://framapic.org/MGABuOpMUDxn/duzY5eaLNVTj.png)
+![Sample image](https://www.planet-casio.com/files/forums/TeX-13737.png)
 
 ## Features
 
-* Build formulae from TeX syntax
+* Build formulae from TeX syntax or using the structural API
 * Highly-customizable graphical and layout parameters
 * Drawing is based on a few user-provided primitives (point, line, text size,
   text)
@@ -26,12 +27,11 @@ List of currently supported elements:
 * Grouping angle brackets, vertical lines, and dots (invisible)
 * Sums, products and integrals (`\sum`, `\prod` and `\int`)
 * Vectors (`\vec`) and limits (`\lim`)
+* Matrices (`\begin{matrix} ... \end{matrix}`)
 
 Features that are partially implemented (and what is left to finish them):
 
 * Support for inline style and display style (expose a parameter)
-* API functions to build TeX objects without a TeX formula (expose functions
-  which are currently in the parser)
 * Full fx-CG 50 support (suitable parenthesis styles)
 
 See the `TODO.md` file for more features to come.
diff --git a/src/env.c b/src/env.c
index dae0856..0603cae 100644
--- a/src/env.c
+++ b/src/env.c
@@ -171,6 +171,8 @@ static void matrix_layout(struct TeX_Env *env)
 		}
 
 		struct TeX_Flow *f = m->elements[i];
+		if(!f) { col++; continue; }
+
 		TeX_flow_layout(f);
 
 		/* Update the current row and column */
@@ -214,7 +216,7 @@ static void matrix_render(struct TeX_Env *env, int x, int y, int color)
 			int cw = m->colwidth[col];
 			int rh = m->rowline[row] + m->rowdepth[row];
 
-			TeX_flow_render(flow,
+			if(flow) TeX_flow_render(flow,
 				x + dx + ((cw - flow->width) >> 1),
 				y + dy + ((rh - flow->height) >> 1),
 				color);